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Abstract:

The present application is directed towards systems and methods for
generating and maintaining cookie consistency for security protection
across a plurality of cores in a multi-core system. A packet processing
engine executing on one core designated as a primary packet processing
engine generates and maintains a global random seed. The global random
seed may be used as an initial seed for creation of cookie signatures by
each of a plurality of packet processing engines executing on a plurality
of cores of the multi-core system using a deterministic pseudo-random
number generation function such that each core creates an identical set
of cookie signatures.

Claims:

1. A method for generating cookie signatures in a multi-core intermediary
providing security protection between a plurality of clients and one or
more servers, the method comprising: (a) establishing, by a first packet
processing engine executing on a first core of an intermediary device
comprising a plurality of packet processing engines executing on a
corresponding core of a plurality of cores, a first cookie timer having a
first predetermined time period, the cookie timer to signal regeneration
of cookie signatures; (b) storing, by the first packet processing engine
responsive to an expiration of the cookie timer, a random seed in shared
memory accessible by each of the plurality of packet processing engines,
a new random seed generated by the first packet processing engine
responsive to each expiration of the cookie timer; (c) storing, by a
second packet processing engine of the plurality of packet processing
engines, the random seed obtained from the shared memory to a cache of
the second packet processing engine; (d) generating, by the second packet
processing engine, one or more cookie signatures based on the random
seed; and (e) determining, by the second packet processing engine
responsive to a second cookie timer established by the second packet
processing engine having a second predetermined timer period less than
the first predetermined time period, whether the random seed in shared
memory has changed in comparison to the random seed stored in the cache
of the second packet processing engine.

2. The method of claim 1, wherein storing a random seed in shared memory
further comprises replacing a previous random seed in shared memory with
the new random seed generated by the first packet processing engine.

3. The method of claim 2, wherein storing a random seed in shared memory
further comprises locking the random seed in shared memory to prevent the
second packet processing engine from reading the seed; replacing the
previous random seed with the new random seed; and unlocking the random
seed.

4. The method of claim 1, wherein generating one or more cookie
signatures based on the random seed further comprises storing a previous
one or more cookie signatures to the cache of the second packet
processing engine as a previous set of cookie signatures prior to
generating the one or more cookie signatures.

5. The method of claim 1, wherein generating one or more cookie
signatures based on the random seed comprises calculating one or more
random numbers using the random seed as an initial value; and storing the
one or more random numbers in an array.

6. The method of claim 1, wherein the first predetermined time period is
two minutes.

7. The method of claim 1, wherein the second predetermined time period is
one second.

8. The method of claim 1, wherein determining whether the random seed in
shared memory has changed in comparison to the random seed stored in the
cache of the second packet processing engine further comprises:
attempting to read the random seed in shared memory; failing to read the
random seed in shared memory, responsive to the random seed being locked
by the first packet processing engine; attempting to read the random seed
in shared memory again; and succeeding to read the random seed in shared
memory, responsive to the random seed being unlocked by the first packet
processing engine.

9. The method of claim 1, further comprising generating, by the second
packet processing engine, one or more transport layer SYN cookies based
on the one or more cookie signatures.

10. The method of claim 1, further comprising generating, by the second
packet processing engine, one or more application layer HTTP cookies
based on the one or more cookie signatures.

11. A method for generating cookie signatures in a multi-core
intermediary providing security protection between a plurality of clients
and one or more servers, the method comprising: (a) generating, by a
second packet processing engine executing on a second core of an
intermediary device comprising a plurality of packet processing engines
executing on a corresponding core of a plurality of cores, a set of
current cookie signatures based on a random seed established by a first
packet processing engine executing on a first core of the plurality of
cores; (b) storing, by the second packet processing engine responsive to
an expiration of a cookie timer, the set of current cookie signatures to
a set of previous cookie signatures; (c) receiving, by the second packet
processing engine, a request from a client to access a server, the
request comprising a cookie; (d) determining, by the second packet
processing engine, that a signature of the cookie does not correspond to
either of the set of previous cookie signatures and the set of current
cookie signatures; (e) generating, by the second packet processing
engine, a second set of current cookie signatures responsive to
identifying that the random seed of the first packet processing engine
has changed; and (f) determining, by the second packet processing engine,
whether to accept the request responsive to whether the cookie signature
of the cookie corresponds to the second set of current cookie signatures.

12. The method of claim 11, wherein generating the set of current cookie
signatures based on a random seed comprises obtaining the random seed
from a shared memory accessible by each of the plurality of packet
processing engines.

13. The method of claim 12, wherein generating the set of current cookie
signatures based on a random seed comprises calculating one or more
random numbers using the random seed as an initial value; and storing the
one or more random numbers in an array.

14. The method of claim 11, wherein storing the set of current cookie
signatures to a set of previous cookie signatures comprises storing the
set of previous cookie signatures in a cache of the second packet
processing engine separate from a shared memory accessible by each of the
plurality of packet processing engines.

15. The method of claim 11, wherein storing the set of current cookie
signatures to a set of previous cookie signatures further comprises
generating a new set of current cookie signatures based on the random
seed.

16. The method of claim 15, wherein storing the set of current cookie
signatures to a set of previous cookie signatures is performed responsive
to determining that the random seed established by the first packet
processing engine has changed.

17. The method of claim 11, wherein receiving a request from a client to
access a server comprises receiving an acknowledgement packet for a
transport layer SYN packet previously transmitted to the client, the
transport layer SYN packet comprising a SYN cookie.

18. The method of claim 17, wherein determining that a signature of the
cookie does not correspond to either of the set of previous cookie
signatures and the set of current cookie signatures further comprises
calculating the signature of the cookie based on the received cookie and
one or more internet layer and transport layer header fields of the
received request.

19. The method of claim 11, wherein receiving a request from a client to
access a server comprises receiving an application layer GET packet
responsive to an application layer data packet previously transmitted to
the client, the application layer data packet comprising an http cookie.

20. The method of claim 11, wherein generating a second set of current
cookie signatures responsive to identifying that the random seed of the
first packet processing engine has changed comprises: identifying that
the random seed established by the first packet processing engine has
changed; obtaining the changed random seed from a shared memory
accessible by each of the plurality of packet processing engines; storing
the set of current cookie signatures to a set of previous cookie
signatures; and generating a second set of current cookie signatures.

Description:

FIELD OF THE INVENTION

[0001] The present application generally relates to data communication
networks. In particular, the present application relates to systems and
methods for generating and maintaining cookie consistency for security
protection across a plurality of cores in a multi-core system.

BACKGROUND OF THE INVENTION

[0002] Synchronization (SYN) attacks, sometimes called SYN floods, and
HTTP Denial of Service (HTTP DoS) attacks are two similar methods that
malicious attackers can use to slow down or disable a remote server by
tying up memory and resources to prevent innocent users from accessing
said resources.

[0003] In the SYN flood or SYN attack, a malicious client or clients send
a plurality of SYN requests. As is usual, the appliance or server
allocates memory and resources for each request and responds with SYN-ACK
messages. The malicious client never responds to these SYN-ACK messages
with acknowledgement messages, and the connections are not established.
Rather, the server or appliance remains in a listening state waiting for
the acknowledgement messages from the client or clients, and the memory
and resources stay allocated to these connections, until the server or
appliance times out, which may be several minutes.

[0004] A similar attack to the SYN flood is the HTTP Denial of Service
(DoS) attack. In this attack, a malicious attacker or attackers establish
legitimate connections with the appliance or server and send HTTP GET
requests for files. In some implementations, the HTTP GET requests are
incomplete requests, which tie up the server or appliance connection
waiting for the remainder of the request until a timeout value expires.
In other implementations, the GET requests are complete requests for very
large files, which are immediately discarded on receipt by the attacker,
who then issues another GET request. In these implementations, the
attacker will frequently spoof or change his IP address, preventing
successful packet filtering solutions. The same behavior can occur
non-maliciously when a breaking news event leads a large number of users
to request the same data simultaneously, overloading the capabilities of
the server.

[0005] In responding to HTTP DoS attacks and SYN flood attacks, one
solution is to create a cookie or cookies that are transmitted to clients
as part of responses and SYN-ACK messages. Because malicious attackers
will discard or not process responses, if a client transmits a request
that includes the cookie, the server or appliance may recognize the
client as a legitimate client. These cookies may be generated using a
random number generator and timers or counters.

BRIEF SUMMARY OF THE INVENTION

[0006] A multi-core system may present complications for this solution,
due to skew of timers, counters, and random numbers between different
cores of the system. For example, one core might transmit a cookie to a
client, the cookie generated using a local random number and/or a local
timer. A response or follow-up request from the client may be directed to
a different core, which may have a different set of cookies due to a
different local random number and/or local timer. Thus, a legitimate
client response may be discarded erroneously as a malicious attack.

[0007] The present application is directed towards systems and methods for
generating and maintaining cookie consistency for security protection
across a plurality of cores in a multi-core system. A packet processing
engine executing on one core designated as a primary packet processing
engine generates and maintains a global random seed. The global random
seed may be used as an initial seed for creation of cookie signatures by
each of a plurality of packet processing engines executing on a plurality
of cores of the multi-core system using a deterministic pseudo-random
number generation function such that each core creates an identical set
of cookie signatures.

[0008] In one aspect, the present invention includes a method for
generating cookie signatures in a multi-core intermediary providing
security protection between a plurality of clients and one or more
servers. The method includes a first packet processing engine executing
on a first core of an intermediary device comprising a plurality of
packet processing engines executing on a corresponding core of a
plurality of cores establishing a first cookie timer having a first
predetermined time period, the cookie timer to signal regeneration of
cookie signatures. The method also includes the first packet processing
engine storing, responsive to an expiration of the cookie timer, a random
seed in shared memory accessible by each of the plurality of packet
processing engines, with a new random seed generated by the first packet
processing engine responsive to each expiration of the cookie timer. The
method further includes a second packet processing engine of the
plurality of packet processing engines, storing the random seed obtained
from the shared memory to a cache of the second packet processing engine.
The method also includes the second packet processing engine, generating
one or more cookie signatures based on the random seed. The method
further includes the second packet processing engine determining,
responsive to a second cookie timer established by the second packet
processing engine having a second predetermined timer period less than
the first predetermined time period, whether the random seed in shared
memory has changed in comparison to the random seed stored in the cache
of the second packet processing engine.

[0009] In some embodiments, the method includes the first packet
processing engine replacing a previous random seed in shared memory with
the new random seed generated by the first packet processing engine. In a
further embodiment, the method includes the first packet processing
engine locking the random seed in shared memory to prevent the second
packet processing engine from reading the see; replacing the previous
random seed with the new random seed; and unlocking the random seed.

[0010] In another embodiment, the method includes the second packet
processing engine storing a previous one or more cookie signatures to the
cache of the second packet processing engine as a previous set of cookie
signatures prior to generating the one or more cookie signatures. In yet
another embodiment, the method includes the second packet processing
engine calculating one or more random numbers using the random seed as an
initial value; and storing the one or more random numbers in an array.

[0011] In one embodiment, the method includes the first predetermined time
period equal to two minutes. In another embodiment, the method includes
the second predetermined time period equal to one second.

[0012] In another embodiment, the method includes the second packet
processing engine attempting to read the random seed in shared memory.
The method also includes the second packet processing engine failing to
read the random seed in shared memory, responsive to the random seed
being locked by the first packet processing engine. The method further
includes the second packet processing engine attempting to read the
random seed in shared memory again. The method further includes the
second packet processing engine succeeding to read the random seed in
shared memory, responsive to the random seed being unlocked by the first
packet processing engine.

[0013] In another embodiment, the method includes the second packet
processing engine generating one or more transport layer SYN cookies
based on the one or more cookie signatures. In yet another embodiment,
the method includes the second packet processing engine generating one or
more application layer HTTP cookies based on the one or more cookie
signatures.

[0014] In another aspect, the present invention includes a method for
generating cookie signatures in a multi-core intermediary providing
security protection between a plurality of clients and one or more
servers. The method includes a second packet processing engine executing
on a second core of an intermediary device comprising a plurality of
packet processing engines executing on a corresponding core of a
plurality of cores generating a set of current cookie signatures based on
a random seed established by a first packet processing engine executing
on a first core of the plurality of cores. The method also includes the
second packet processing engine storing, responsive to an expiration of a
cookie timer, the set of current cookie signatures to a set of previous
cookie signatures. The method also includes the second packet processing
engine receiving a request from a client to access a server, the request
comprising a cookie. The method further includes the second packet
processing engine determining that a signature of the cookie does not
correspond to either of the set of previous cookie signatures and the set
of current cookie signatures. The method also includes the second packet
processing engine generating a second set of current cookie signatures
responsive to identifying that the random seed of the first packet
processing engine has changed. The method also includes the second packet
processing engine determining whether to accept the request responsive to
whether the cookie signature of the cookie corresponds to the second set
of current cookie signatures.

[0015] In some embodiments, the method includes the second packet
processing engine obtaining the random seed from a shared memory
accessible by each of the plurality of packet processing engines. In a
further embodiment, the method includes the second packet processing
engine calculating one or more random numbers using the random seed as an
initial value; and storing the one or more random numbers in an array.

[0016] In another embodiment, the method includes the second packet
processing engine storing the set of previous cookie signatures in a
cache of the second packet processing engine separate from a shared
memory accessible by each of the plurality of packet processing engines.
In yet another embodiment, the method includes the second packet
processing engine generating a new set of current cookie signatures based
on the random seed. In a further embodiment, the method includes the
second packet processing engine storing the set of current cookie
signatures to a set of previous cookie signatures, responsive to
determining that the random seed established by the first packet
processing engine has changed.

[0017] In another embodiment, the method includes the second packet
processing engine receiving an acknowledgement packet for a transport
layer SYN packet previously transmitted to the client, the transport
layer SYN packet comprising a SYN cookie. In a further embodiment, the
method includes the second packet processing engine calculating the
signature of the cookie based on the received cookie and one or more
internet layer and transport layer header fields of the received request.

[0018] In yet another embodiment, the method includes the second packet
processing engine receiving an application layer GET packet responsive to
an application layer data packet previously transmitted to the client,
the application layer data packet comprising an http cookie.

[0019] In still another embodiment, the method includes the second packet
processing engine identifying that the random seed established by the
first packet processing engine has changed. The method also includes the
second packet processing engine obtaining the changed random seed from a
shared memory accessible by each of the plurality of packet processing
engines. The method further includes the second packet processing engine
storing the set of current cookie signatures to a set of previous cookie
signatures. The method also includes the second packet processing engine
generating a second set of current cookie signatures.

[0020] The details of various embodiments of the invention are set forth
in the accompanying drawings and the description below.

BRIEF DESCRIPTION OF THE FIGURES

[0021] The foregoing and other objects, aspects, features, and advantages
of the invention will become more apparent and better understood by
referring to the following description taken in conjunction with the
accompanying drawings, in which:

[0022] FIG. 1A is a block diagram of an embodiment of a network
environment for a client to access a server via an appliance;

[0023] FIG. 1B is a block diagram of an embodiment of an environment for
delivering a computing environment from a server to a client via an
appliance;

[0024] FIG. 1C is a block diagram of another embodiment of an environment
for delivering a computing environment from a server to a client via an
appliance;

[0025] FIG. 1D is a block diagram of another embodiment of an environment
for delivering a computing environment from a server to a client via an
appliance;

[0026] FIGS. 1E-1H are block diagrams of embodiments of a computing
device;

[0027] FIG. 2A is a block diagram of an embodiment of an appliance for
processing communications between a client and a server;

[0028] FIG. 2B is a block diagram of another embodiment of an appliance
for optimizing, accelerating, load-balancing and routing communications
between a client and a server;

[0029] FIG. 3 is a block diagram of an embodiment of a client for
communicating with a server via the appliance;

[0030] FIG. 4A is a block diagram of an embodiment of a virtualization
environment;

[0031] FIG. 4B is a block diagram of another embodiment of a
virtualization environment;

[0032] FIG. 4C is a block diagram of an embodiment of a virtualized
appliance;

[0033] FIG. 5A are block diagrams of embodiments of approaches to
implementing parallelism in a multi-core system;

[0034] FIG. 5B is a block diagram of an embodiment of a system utilizing a
multi-core system;

[0035] FIG. 5C is a block diagram of another embodiment of an aspect of a
multi-core system;

[0036] FIG. 6 is a block diagram of an embodiment of a multi-core system
for generating cookie signatures;

[0037]FIG. 7A is a flow chart of an embodiment of a method of generating
and maintaining consistent cookie signatures in a multi-core system; and

[0038] FIG. 7B is a flow chart of an embodiment of a method of using
cookie signatures for security in a multi-core system.

[0039] The features and advantages of the present invention will become
more apparent from the detailed description set forth below when taken in
conjunction with the drawings, in which like reference characters
identify corresponding elements throughout. In the drawings, like
reference numbers generally indicate identical, functionally similar,
and/or structurally similar elements.

DETAILED DESCRIPTION OF THE INVENTION

[0040] For purposes of reading the description of the various embodiments
below, the following descriptions of the sections of the specification
and their respective contents may be helpful: [0041] Section A
describes a network environment and computing environment which may be
useful for practicing embodiments described herein; [0042] Section B
describes embodiments of systems and methods for delivering a computing
environment to a remote user; [0043] Section C describes embodiments of
systems and methods for accelerating communications between a client and
a server; [0044] Section D describes embodiments of systems and methods
for virtualizing an application delivery controller; [0045] Section E
describes embodiments of systems and methods for providing a multi-core
architecture and environment; and [0046] Section F describes embodiments
of systems and methods for generating cookie signatures for security
protection in a multi-core system.

A. Network and Computing Environment

[0047] Prior to discussing the specifics of embodiments of the systems and
methods of an appliance and/or client, it may be helpful to discuss the
network and computing environments in which such embodiments may be
deployed. Referring now to FIG. 1A, an embodiment of a network
environment is depicted. In brief overview, the network environment
comprises one or more clients 102a-102n (also generally referred to as
local machine(s) 102, or client(s) 102) in communication with one or more
servers 106a-106n (also generally referred to as server(s) 106, or remote
machine(s) 106) via one or more networks 104, 104' (generally referred to
as network 104). In some embodiments, a client 102 communicates with a
server 106 via an appliance 200.

[0048] Although FIG. 1A shows a network 104 and a network 104' between the
clients 102 and the servers 106, the clients 102 and the servers 106 may
be on the same network 104. The networks 104 and 104' can be the same
type of network or different types of networks. The network 104 and/or
the network 104' can be a local-area network (LAN), such as a company
Intranet, a metropolitan area network (MAN), or a wide area network
(WAN), such as the Internet or the World Wide Web. In one embodiment,
network 104' may be a private network and network 104 may be a public
network. In some embodiments, network 104 may be a private network and
network 104' a public network. In another embodiment, networks 104 and
104' may both be private networks. In some embodiments, clients 102 may
be located at a branch office of a corporate enterprise communicating via
a WAN connection over the network 104 to the servers 106 located at a
corporate data center.

[0049] The network 104 and/or 104' be any type and/or form of network and
may include any of the following: a point to point network, a broadcast
network, a wide area network, a local area network, a telecommunications
network, a data communication network, a computer network, an ATM
(Asynchronous Transfer Mode) network, a SONET (Synchronous Optical
Network) network, a SDH (Synchronous Digital Hierarchy) network, a
wireless network and a wireline network. In some embodiments, the network
104 may comprise a wireless link, such as an infrared channel or
satellite band. The topology of the network 104 and/or 104' may be a bus,
star, or ring network topology. The network 104 and/or 104' and network
topology may be of any such network or network topology as known to those
ordinarily skilled in the art capable of supporting the operations
described herein.

[0050] As shown in FIG. 1A, the appliance 200, which also may be referred
to as an interface unit 200 or gateway 200, is shown between the networks
104 and 104'. In some embodiments, the appliance 200 may be located on
network 104. For example, a branch office of a corporate enterprise may
deploy an appliance 200 at the branch office. In other embodiments, the
appliance 200 may be located on network 104'. For example, an appliance
200 may be located at a corporate data center. In yet another embodiment,
a plurality of appliances 200 may be deployed on network 104. In some
embodiments, a plurality of appliances 200 may be deployed on network
104'. In one embodiment, a first appliance 200 communicates with a second
appliance 200'. In other embodiments, the appliance 200 could be a part
of any client 102 or server 106 on the same or different network 104,104'
as the client 102. One or more appliances 200 may be located at any point
in the network or network communications path between a client 102 and a
server 106.

[0051] In some embodiments, the appliance 200 comprises any of the network
devices manufactured by Citrix Systems, Inc. of Ft. Lauderdale Fla.,
referred to as Citrix NetScaler devices. In other embodiments, the
appliance 200 includes any of the product embodiments referred to as
WebAccelerator and BigIP manufactured by F5 Networks, Inc. of Seattle,
Wash. In another embodiment, the appliance 205 includes any of the DX
acceleration device platforms and/or the SSL VPN series of devices, such
as SA 700, SA 2000, SA 4000, and SA 6000 devices manufactured by Juniper
Networks, Inc. of Sunnyvale, Calif. In yet another embodiment, the
appliance 200 includes any application acceleration and/or security
related appliances and/or software manufactured by Cisco Systems, Inc. of
San Jose, Calif., such as the Cisco ACE Application Control Engine Module
service software and network modules, and Cisco AVS Series Application
Velocity System.

[0052] In one embodiment, the system may include multiple,
logically-grouped servers 106. In these embodiments, the logical group of
servers may be referred to as a server farm 38. In some of these
embodiments, the serves 106 may be geographically dispersed. In some
cases, a farm 38 may be administered as a single entity. In other
embodiments, the server farm 38 comprises a plurality of server farms 38.
In one embodiment, the server farm executes one or more applications on
behalf of one or more clients 102.

[0053] The servers 106 within each farm 38 can be heterogeneous. One or
more of the servers 106 can operate according to one type of operating
system platform (e.g., WINDOWS NT, manufactured by Microsoft Corp. of
Redmond, Wash.), while one or more of the other servers 106 can operate
on according to another type of operating system platform (e.g., Unix or
Linux). The servers 106 of each farm 38 do not need to be physically
proximate to another server 106 in the same farm 38. Thus, the group of
servers 106 logically grouped as a farm 38 may be interconnected using a
wide-area network (WAN) connection or medium-area network (MAN)
connection. For example, a farm 38 may include servers 106 physically
located in different continents or different regions of a continent,
country, state, city, campus, or room. Data transmission speeds between
servers 106 in the farm 38 can be increased if the servers 106 are
connected using a local-area network (LAN) connection or some form of
direct connection.

[0054] Servers 106 may be referred to as a file server, application
server, web server, proxy server, or gateway server. In some embodiments,
a server 106 may have the capacity to function as either an application
server or as a master application server. In one embodiment, a server 106
may include an Active Directory. The clients 102 may also be referred to
as client nodes or endpoints. In some embodiments, a client 102 has the
capacity to function as both a client node seeking access to applications
on a server and as an application server providing access to hosted
applications for other clients 102a-102n.

[0055] In some embodiments, a client 102 communicates with a server 106.
In one embodiment, the client 102 communicates directly with one of the
servers 106 in a farm 38. In another embodiment, the client 102 executes
a program neighborhood application to communicate with a server 106 in a
farm 38. In still another embodiment, the server 106 provides the
functionality of a master node. In some embodiments, the client 102
communicates with the server 106 in the farm 38 through a network 104.
Over the network 104, the client 102 can, for example, request execution
of various applications hosted by the servers 106a-106n in the farm 38
and receive output of the results of the application execution for
display. In some embodiments, only the master node provides the
functionality required to identify and provide address information
associated with a server 106' hosting a requested application.

[0056] In one embodiment, the server 106 provides functionality of a web
server. In another embodiment, the server 106a receives requests from the
client 102, forwards the requests to a second server 106b and responds to
the request by the client 102 with a response to the request from the
server 106b. In still another embodiment, the server 106 acquires an
enumeration of applications available to the client 102 and address
information associated with a server 106 hosting an application
identified by the enumeration of applications. In yet another embodiment,
the server 106 presents the response to the request to the client 102
using a web interface. In one embodiment, the client 102 communicates
directly with the server 106 to access the identified application. In
another embodiment, the client 102 receives application output data, such
as display data, generated by an execution of the identified application
on the server 106.

[0057] Referring now to FIG. 1B, an embodiment of a network environment
deploying multiple appliances 200 is depicted. A first appliance 200 may
be deployed on a first network 104 and a second appliance 200' on a
second network 104'. For example a corporate enterprise may deploy a
first appliance 200 at a branch office and a second appliance 200' at a
data center. In another embodiment, the first appliance 200 and second
appliance 200' are deployed on the same network 104 or network 104. For
example, a first appliance 200 may be deployed for a first server farm
38, and a second appliance 200 may be deployed for a second server farm
38'. In another example, a first appliance 200 may be deployed at a first
branch office while the second appliance 200' is deployed at a second
branch office'. In some embodiments, the first appliance 200 and second
appliance 200' work in cooperation or in conjunction with each other to
accelerate network traffic or the delivery of application and data
between a client and a server

[0058] Referring now to FIG. 1C, another embodiment of a network
environment deploying the appliance 200 with one or more other types of
appliances, such as between one or more WAN optimization appliance 205,
205' is depicted. For example a first WAN optimization appliance 205 is
shown between networks 104 and 104' and a second WAN optimization
appliance 205' may be deployed between the appliance 200 and one or more
servers 106. By way of example, a corporate enterprise may deploy a first
WAN optimization appliance 205 at a branch office and a second WAN
optimization appliance 205' at a data center. In some embodiments, the
appliance 205 may be located on network 104'. In other embodiments, the
appliance 205' may be located on network 104. In some embodiments, the
appliance 205' may be located on network 104' or network 104''. In one
embodiment, the appliance 205 and 205' are on the same network. In
another embodiment, the appliance 205 and 205' are on different networks.
In another example, a first WAN optimization appliance 205 may be
deployed for a first server farm 38 and a second WAN optimization
appliance 205' for a second server farm 38'

[0059] In one embodiment, the appliance 205 is a device for accelerating,
optimizing or otherwise improving the performance, operation, or quality
of service of any type and form of network traffic, such as traffic to
and/or from a WAN connection. In some embodiments, the appliance 205 is a
performance enhancing proxy. In other embodiments, the appliance 205 is
any type and form of WAN optimization or acceleration device, sometimes
also referred to as a WAN optimization controller. In one embodiment, the
appliance 205 is any of the product embodiments referred to as WANScaler
manufactured by Citrix Systems, Inc. of Ft. Lauderdale, Fla. In other
embodiments, the appliance 205 includes any of the product embodiments
referred to as BIG-IP link controller and WANjet manufactured by F5
Networks, Inc. of Seattle, Wash. In another embodiment, the appliance 205
includes any of the WX and WXC WAN acceleration device platforms
manufactured by Juniper Networks, Inc. of Sunnyvale, Calif. In some
embodiments, the appliance 205 includes any of the steelhead line of WAN
optimization appliances manufactured by Riverbed Technology of San
Francisco, Calif. In other embodiments, the appliance 205 includes any of
the WAN related devices manufactured by Expand Networks Inc. of Roseland,
N.J. In one embodiment, the appliance 205 includes any of the WAN related
appliances manufactured by Packeteer Inc. of Cupertino, Calif., such as
the PacketShaper, iShared, and SkyX product embodiments provided by
Packeteer. In yet another embodiment, the appliance 205 includes any WAN
related appliances and/or software manufactured by Cisco Systems, Inc. of
San Jose, Calif., such as the Cisco Wide Area Network Application
Services software and network modules, and Wide Area Network engine
appliances.

[0060] In one embodiment, the appliance 205 provides application and data
acceleration services for branch-office or remote offices. In one
embodiment, the appliance 205 includes optimization of Wide Area File
Services (WAFS). In another embodiment, the appliance 205 accelerates the
delivery of files, such as via the Common Internet File System (CIFS)
protocol. In other embodiments, the appliance 205 provides caching in
memory and/or storage to accelerate delivery of applications and data. In
one embodiment, the appliance 205 provides compression of network traffic
at any level of the network stack or at any protocol or network layer. In
another embodiment, the appliance 205 provides transport layer protocol
optimizations, flow control, performance enhancements or modifications
and/or management to accelerate delivery of applications and data over a
WAN connection. For example, in one embodiment, the appliance 205
provides Transport Control Protocol (TCP) optimizations. In other
embodiments, the appliance 205 provides optimizations, flow control,
performance enhancements or modifications and/or management for any
session or application layer protocol.

[0061] In another embodiment, the appliance 205 encoded any type and form
of data or information into custom or standard TCP and/or IP header
fields or option fields of network packet to announce presence,
functionality or capability to another appliance 205'. In another
embodiment, an appliance 205' may communicate with another appliance 205'
using data encoded in both TCP and/or IP header fields or options. For
example, the appliance may use TCP option(s) or IP header fields or
options to communicate one or more parameters to be used by the
appliances 205, 205' in performing functionality, such as WAN
acceleration, or for working in conjunction with each other.

[0062] In some embodiments, the appliance 200 preserves any of the
information encoded in TCP and/or IP header and/or option fields
communicated between appliances 205 and 205'. For example, the appliance
200 may terminate a transport layer connection traversing the appliance
200, such as a transport layer connection from between a client and a
server traversing appliances 205 and 205'. In one embodiment, the
appliance 200 identifies and preserves any encoded information in a
transport layer packet transmitted by a first appliance 205 via a first
transport layer connection and communicates a transport layer packet with
the encoded information to a second appliance 205' via a second transport
layer connection.

[0063] Referring now to FIG. 1D, a network environment for delivering
and/or operating a computing environment on a client 102 is depicted. In
some embodiments, a server 106 includes an application delivery system
190 for delivering a computing environment or an application and/or data
file to one or more clients 102. In brief overview, a client 10 is in
communication with a server 106 via network 104, 104' and appliance 200.
For example, the client 102 may reside in a remote office of a company,
e.g., a branch office, and the server 106 may reside at a corporate data
center. The client 102 comprises a client agent 120, and a computing
environment 15. The computing environment 15 may execute or operate an
application that accesses, processes or uses a data file. The computing
environment 15, application and/or data file may be delivered via the
appliance 200 and/or the server 106.

[0064] In some embodiments, the appliance 200 accelerates delivery of a
computing environment 15, or any portion thereof, to a client 102. In one
embodiment, the appliance 200 accelerates the delivery of the computing
environment 15 by the application delivery system 190. For example, the
embodiments described herein may be used to accelerate delivery of a
streaming application and data file processable by the application from a
central corporate data center to a remote user location, such as a branch
office of the company. In another embodiment, the appliance 200
accelerates transport layer traffic between a client 102 and a server
106. The appliance 200 may provide acceleration techniques for
accelerating any transport layer payload from a server 106 to a client
102, such as: 1) transport layer connection pooling, 2) transport layer
connection multiplexing, 3) transport control protocol buffering, 4)
compression and 5) caching. In some embodiments, the appliance 200
provides load balancing of servers 106 in responding to requests from
clients 102. In other embodiments, the appliance 200 acts as a proxy or
access server to provide access to the one or more servers 106. In
another embodiment, the appliance 200 provides a secure virtual private
network connection from a first network 104 of the client 102 to the
second network 104' of the server 106, such as an SSL VPN connection. It
yet other embodiments, the appliance 200 provides application firewall
security, control and management of the connection and communications
between a client 102 and a server 106.

[0065] In some embodiments, the application delivery management system 190
provides application delivery techniques to deliver a computing
environment to a desktop of a user, remote or otherwise, based on a
plurality of execution methods and based on any authentication and
authorization policies applied via a policy engine 195. With these
techniques, a remote user may obtain a computing environment and access
to server stored applications and data files from any network connected
device 100. In one embodiment, the application delivery system 190 may
reside or execute on a server 106. In another embodiment, the application
delivery system 190 may reside or execute on a plurality of servers
106a-106n. In some embodiments, the application delivery system 190 may
execute in a server farm 38. In one embodiment, the server 106 executing
the application delivery system 190 may also store or provide the
application and data file. In another embodiment, a first set of one or
more servers 106 may execute the application delivery system 190, and a
different server 106n may store or provide the application and data file.
In some embodiments, each of the application delivery system 190, the
application, and data file may reside or be located on different servers.
In yet another embodiment, any portion of the application delivery system
190 may reside, execute or be stored on or distributed to the appliance
200, or a plurality of appliances.

[0066] The client 102 may include a computing environment 15 for executing
an application that uses or processes a data file. The client 102 via
networks 104, 104' and appliance 200 may request an application and data
file from the server 106. In one embodiment, the appliance 200 may
forward a request from the client 102 to the server 106. For example, the
client 102 may not have the application and data file stored or
accessible locally. In response to the request, the application delivery
system 190 and/or server 106 may deliver the application and data file to
the client 102. For example, in one embodiment, the server 106 may
transmit the application as an application stream to operate in computing
environment 15 on client 102.

[0067] In some embodiments, the application delivery system 190 comprises
any portion of the Citrix Access Suite® by Citrix Systems, Inc., such
as the MetaFrame or Citrix Presentation Server® and/or any of the
Microsoft® Windows Terminal Services manufactured by the Microsoft
Corporation. In one embodiment, the application delivery system 190 may
deliver one or more applications to clients 102 or users via a
remote-display protocol or otherwise via remote-based or server-based
computing. In another embodiment, the application delivery system 190 may
deliver one or more applications to clients or users via steaming of the
application.

[0068] In one embodiment, the application delivery system 190 includes a
policy engine 195 for controlling and managing the access to, selection
of application execution methods and the delivery of applications. In
some embodiments, the policy engine 195 determines the one or more
applications a user or client 102 may access. In another embodiment, the
policy engine 195 determines how the application should be delivered to
the user or client 102, e.g., the method of execution. In some
embodiments, the application delivery system 190 provides a plurality of
delivery techniques from which to select a method of application
execution, such as a server-based computing, streaming or delivering the
application locally to the client 120 for local execution.

[0069] In one embodiment, a client 102 requests execution of an
application program and the application delivery system 190 comprising a
server 106 selects a method of executing the application program. In some
embodiments, the server 106 receives credentials from the client 102. In
another embodiment, the server 106 receives a request for an enumeration
of available applications from the client 102. In one embodiment, in
response to the request or receipt of credentials, the application
delivery system 190 enumerates a plurality of application programs
available to the client 102. The application delivery system 190 receives
a request to execute an enumerated application. The application delivery
system 190 selects one of a predetermined number of methods for executing
the enumerated application, for example, responsive to a policy of a
policy engine. The application delivery system 190 may select a method of
execution of the application enabling the client 102 to receive
application-output data generated by execution of the application program
on a server 106. The application delivery system 190 may select a method
of execution of the application enabling the local machine 10 to execute
the application program locally after retrieving a plurality of
application files comprising the application. In yet another embodiment,
the application delivery system 190 may select a method of execution of
the application to stream the application via the network 104 to the
client 102.

[0070] A client 102 may execute, operate or otherwise provide an
application, which can be any type and/or form of software, program, or
executable instructions such as any type and/or form of web browser,
web-based client, client-server application, a thin-client computing
client, an ActiveX control, or a Java applet, or any other type and/or
form of executable instructions capable of executing on client 102. In
some embodiments, the application may be a server-based or a remote-based
application executed on behalf of the client 102 on a server 106. In one
embodiments the server 106 may display output to the client 102 using any
thin-client or remote-display protocol, such as the Independent Computing
Architecture (ICA) protocol manufactured by Citrix Systems, Inc. of Ft.
Lauderdale, Fla. or the Remote Desktop Protocol (RDP) manufactured by the
Microsoft Corporation of Redmond, Wash. The application can use any type
of protocol and it can be, for example, an HTTP client, an FTP client, an
Oscar client, or a Telnet client. In other embodiments, the application
comprises any type of software related to VoIP communications, such as a
soft IP telephone. In further embodiments, the application comprises any
application related to real-time data communications, such as
applications for streaming video and/or audio.

[0071] In some embodiments, the server 106 or a server farm 38 may be
running one or more applications, such as an application providing a
thin-client computing or remote display presentation application. In one
embodiment, the server 106 or server farm 38 executes as an application,
any portion of the Citrix Access Suite® by Citrix Systems, Inc., such
as the MetaFrame or Citrix Presentation Server®, and/or any of the
Microsoft® Windows Terminal Services manufactured by the Microsoft
Corporation. In one embodiment, the application is an ICA client,
developed by Citrix Systems, Inc. of Fort Lauderdale, Fla. In other
embodiments, the application includes a Remote Desktop (RDP) client,
developed by Microsoft Corporation of Redmond, Wash. Also, the server 106
may run an application, which for example, may be an application server
providing email services such as Microsoft Exchange manufactured by the
Microsoft Corporation of Redmond, Wash., a web or Internet server, or a
desktop sharing server, or a collaboration server. In some embodiments,
any of the applications may comprise any type of hosted service or
products, such as GoToMeeting® provided by Citrix Online Division,
Inc. of Santa Barbara, California, WebEx® provided by WebEx, Inc. of
Santa Clara, Calif., or Microsoft Office Live Meeting provided by
Microsoft Corporation of Redmond, Wash.

[0072] Still referring to FIG. 1D, an embodiment of the network
environment may include a monitoring server 106A. The monitoring server
106A may include any type and form performance monitoring service 198.
The performance monitoring service 198 may include monitoring,
measurement and/or management software and/or hardware, including data
collection, aggregation, analysis, management and reporting. In one
embodiment, the performance monitoring service 198 includes one or more
monitoring agents 197. The monitoring agent 197 includes any software,
hardware or combination thereof for performing monitoring, measurement
and data collection activities on a device, such as a client 102, server
106 or an appliance 200, 205. In some embodiments, the monitoring agent
197 includes any type and form of script, such as Visual Basic script, or
Javascript. In one embodiment, the monitoring agent 197 executes
transparently to any application and/or user of the device. In some
embodiments, the monitoring agent 197 is installed and operated
unobtrusively to the application or client. In yet another embodiment,
the monitoring agent 197 is installed and operated without any
instrumentation for the application or device.

[0073] In some embodiments, the monitoring agent 197 monitors, measures
and collects data on a predetermined frequency. In other embodiments, the
monitoring agent 197 monitors, measures and collects data based upon
detection of any type and form of event. For example, the monitoring
agent 197 may collect data upon detection of a request for a web page or
receipt of an HTTP response. In another example, the monitoring agent 197
may collect data upon detection of any user input events, such as a mouse
click. The monitoring agent 197 may report or provide any monitored,
measured or collected data to the monitoring service 198. In one
embodiment, the monitoring agent 197 transmits information to the
monitoring service 198 according to a schedule or a predetermined
frequency. In another embodiment, the monitoring agent 197 transmits
information to the monitoring service 198 upon detection of an event.

[0074] In some embodiments, the monitoring service 198 and/or monitoring
agent 197 performs monitoring and performance measurement of any network
resource or network infrastructure element, such as a client, server,
server farm, appliance 200, appliance 205, or network connection. In one
embodiment, the monitoring service 198 and/or monitoring agent 197
performs monitoring and performance measurement of any transport layer
connection, such as a TCP or UDP connection. In another embodiment, the
monitoring service 198 and/or monitoring agent 197 monitors and measures
network latency. In yet one embodiment, the monitoring service 198 and/or
monitoring agent 197 monitors and measures bandwidth utilization.

[0075] In other embodiments, the monitoring service 198 and/or monitoring
agent 197 monitors and measures end-user response times. In some
embodiments, the monitoring service 198 performs monitoring and
performance measurement of an application. In another embodiment, the
monitoring service 198 and/or monitoring agent 197 performs monitoring
and performance measurement of any session or connection to the
application. In one embodiment, the monitoring service 198 and/or
monitoring agent 197 monitors and measures performance of a browser. In
another embodiment, the monitoring service 198 and/or monitoring agent
197 monitors and measures performance of HTTP based transactions. In some
embodiments, the monitoring service 198 and/or monitoring agent 197
monitors and measures performance of a Voice over IP (VoIP) application
or session. In other embodiments, the monitoring service 198 and/or
monitoring agent 197 monitors and measures performance of a remote
display protocol application, such as an ICA client or RDP client. In yet
another embodiment, the monitoring service 198 and/or monitoring agent
197 monitors and measures performance of any type and form of streaming
media. In still a further embodiment, the monitoring service 198 and/or
monitoring agent 197 monitors and measures performance of a hosted
application or a Software-As-A-Service (SaaS) delivery model.

[0076] In some embodiments, the monitoring service 198 and/or monitoring
agent 197 performs monitoring and performance measurement of one or more
transactions, requests or responses related to application. In other
embodiments, the monitoring service 198 and/or monitoring agent 197
monitors and measures any portion of an application layer stack, such as
any .NET or J2EE calls. In one embodiment, the monitoring service 198
and/or monitoring agent 197 monitors and measures database or SQL
transactions. In yet another embodiment, the monitoring service 198
and/or monitoring agent 197 monitors and measures any method, function or
application programming interface (API) call.

[0077] In one embodiment, the monitoring service 198 and/or monitoring
agent 197 performs monitoring and performance measurement of a delivery
of application and/or data from a server to a client via one or more
appliances, such as appliance 200 and/or appliance 205. In some
embodiments, the monitoring service 198 and/or monitoring agent 197
monitors and measures performance of delivery of a virtualized
application. In other embodiments, the monitoring service 198 and/or
monitoring agent 197 monitors and measures performance of delivery of a
streaming application. In another embodiment, the monitoring service 198
and/or monitoring agent 197 monitors and measures performance of delivery
of a desktop application to a client and/or the execution of the desktop
application on the client. In another embodiment, the monitoring service
198 and/or monitoring agent 197 monitors and measures performance of a
client/server application.

[0078] In one embodiment, the monitoring service 198 and/or monitoring
agent 197 is designed and constructed to provide application performance
management for the application delivery system 190. For example, the
monitoring service 198 and/or monitoring agent 197 may monitor, measure
and manage the performance of the delivery of applications via the Citrix
Presentation Server. In this example, the monitoring service 198 and/or
monitoring agent 197 monitors individual ICA sessions. The monitoring
service 198 and/or monitoring agent 197 may measure the total and per
session system resource usage, as well as application and networking
performance. The monitoring service 198 and/or monitoring agent 197 may
identify the active servers for a given user and/or user session. In some
embodiments, the monitoring service 198 and/or monitoring agent 197
monitors back-end connections between the application delivery system 190
and an application and/or database server. The monitoring service 198
and/or monitoring agent 197 may measure network latency, delay and volume
per user-session or ICA session.

[0079] In some embodiments, the monitoring service 198 and/or monitoring
agent 197 measures and monitors memory usage for the application delivery
system 190, such as total memory usage, per user session and/or per
process. In other embodiments, the monitoring service 198 and/or
monitoring agent 197 measures and monitors CPU usage the application
delivery system 190, such as total CPU usage, per user session and/or per
process. In another embodiments, the monitoring service 198 and/or
monitoring agent 197 measures and monitors the time required to log-in to
an application, a server, or the application delivery system, such as
Citrix Presentation Server. In one embodiment, the monitoring service 198
and/or monitoring agent 197 measures and monitors the duration a user is
logged into an application, a server, or the application delivery system
190. In some embodiments, the monitoring service 198 and/or monitoring
agent 197 measures and monitors active and inactive session counts for an
application, server or application delivery system session. In yet
another embodiment, the monitoring service 198 and/or monitoring agent
197 measures and monitors user session latency.

[0080] In yet further embodiments, the monitoring service 198 and/or
monitoring agent 197 measures and monitors measures and monitors any type
and form of server metrics. In one embodiment, the monitoring service 198
and/or monitoring agent 197 measures and monitors metrics related to
system memory, CPU usage, and disk storage. In another embodiment, the
monitoring service 198 and/or monitoring agent 197 measures and monitors
metrics related to page faults, such as page faults per second. In other
embodiments, the monitoring service 198 and/or monitoring agent 197
measures and monitors round-trip time metrics. In yet another embodiment,
the monitoring service 198 and/or monitoring agent 197 measures and
monitors metrics related to application crashes, errors and/or hangs.

[0081] In some embodiments, the monitoring service 198 and monitoring
agent 198 includes any of the product embodiments referred to as
EdgeSight manufactured by Citrix Systems, Inc. of Ft. Lauderdale, Fla. In
another embodiment, the performance monitoring service 198 and/or
monitoring agent 198 includes any portion of the product embodiments
referred to as the TrueView product suite manufactured by the Symphoniq
Corporation of Palo Alto, Calif. In one embodiment, the performance
monitoring service 198 and/or monitoring agent 198 includes any portion
of the product embodiments referred to as the TeaLeaf CX product suite
manufactured by the TeaLeaf Technology Inc. of San Francisco, Calif. In
other embodiments, the performance monitoring service 198 and/or
monitoring agent 198 includes any portion of the business service
management products, such as the BMC Performance Manager and Patrol
products, manufactured by BMC Software, Inc. of Houston, Tex.

[0082] The client 102, server 106, and appliance 200 may be deployed as
and/or executed on any type and form of computing device, such as a
computer, network device or appliance capable of communicating on any
type and form of network and performing the operations described herein.
FIGS. 1E and 1F depict block diagrams of a computing device 100 useful
for practicing an embodiment of the client 102, server 106 or appliance
200. As shown in FIGS. 1E and 1F, each computing device 100 includes a
central processing unit 101, and a main memory unit 122. As shown in FIG.
1E, a computing device 100 may include a visual display device 124, a
keyboard 126 and/or a pointing device 127, such as a mouse. Each
computing device 100 may also include additional optional elements, such
as one or more input/output devices 130a-130b (generally referred to
using reference numeral 130), and a cache memory 140 in communication
with the central processing unit 101.

[0083] The central processing unit 101 is any logic circuitry that
responds to and processes instructions fetched from the main memory unit
122. In many embodiments, the central processing unit is provided by a
microprocessor unit, such as: those manufactured by Intel Corporation of
Mountain View, Calif.; those manufactured by Motorola Corporation of
Schaumburg, Ill.; those manufactured by Transmeta Corporation of Santa
Clara, Calif.; the RS/6000 processor, those manufactured by International
Business Machines of White Plains, N.Y.; or those manufactured by
Advanced Micro Devices of Sunnyvale, Calif. The computing device 100 may
be based on any of these processors, or any other processor capable of
operating as described herein.

[0084] Main memory unit 122 may be one or more memory chips capable of
storing data and allowing any storage location to be directly accessed by
the microprocessor 101, such as Static random access memory (SRAM), Burst
SRAM or SynchBurst SRAM (BSRAM), Dynamic random access memory (DRAM),
Fast Page Mode DRAM (FPM DRAM), Enhanced DRAM (EDRAM), Extended Data
Output RAM (EDO RAM), Extended Data Output DRAM (EDO DRAM), Burst
Extended Data Output DRAM (BEDO DRAM), Enhanced DRAM (EDRAM), synchronous
DRAM (SDRAM), JEDEC SRAM, PC100 SDRAM, Double Data Rate SDRAM (DDR
SDRAM), Enhanced SDRAM (ESDRAM), SyncLink DRAM (SLDRAM), Direct Rambus
DRAM (DRDRAM), or Ferroelectric RAM (FRAM). The main memory 122 may be
based on any of the above described memory chips, or any other available
memory chips capable of operating as described herein. In the embodiment
shown in FIG. 1E, the processor 101 communicates with main memory 122 via
a system bus 150 (described in more detail below). FIG. 1F depicts an
embodiment of a computing device 100 in which the processor communicates
directly with main memory 122 via a memory port 103. For example, in FIG.
1F the main memory 122 may be DRDRAM.

[0085] FIG. 1F depicts an embodiment in which the main processor 101
communicates directly with cache memory 140 via a secondary bus,
sometimes referred to as a backside bus. In other embodiments, the main
processor 101 communicates with cache memory 140 using the system bus
150. Cache memory 140 typically has a faster response time than main
memory 122 and is typically provided by SRAM, BSRAM, or EDRAM. In the
embodiment shown in FIG. 1F, the processor 101 communicates with various
I/O devices 130 via a local system bus 150. Various busses may be used to
connect the central processing unit 101 to any of the I/O devices 130,
including a VESA VL bus, an ISA bus, an EISA bus, a MicroChannel
Architecture (MCA) bus, a PCI bus, a PCI-X bus, a PCI-Express bus, or a
NuBus. For embodiments in which the I/O device is a video display 124,
the processor 101 may use an Advanced Graphics Port (AGP) to communicate
with the display 124. FIG. 1F depicts an embodiment of a computer 100 in
which the main processor 101 communicates directly with I/O device 130b
via HyperTransport, Rapid I/O, or InfiniBand. FIG. 1F also depicts an
embodiment in which local busses and direct communication are mixed: the
processor 101 communicates with I/O device 130b using a local
interconnect bus while communicating with I/O device 130a directly.

[0086] The computing device 100 may support any suitable installation
device 116, such as a floppy disk drive for receiving floppy disks such
as 3.5-inch, 5.25-inch disks or ZIP disks, a CD-ROM drive, a CD-R/RW
drive, a DVD-ROM drive, tape drives of various formats, USB device,
hard-drive or any other device suitable for installing software and
programs such as any client agent 120, or portion thereof. The computing
device 100 may further comprise a storage device 128, such as one or more
hard disk drives or redundant arrays of independent disks, for storing an
operating system and other related software, and for storing application
software programs such as any program related to the client agent 120.
Optionally, any of the installation devices 116 could also be used as the
storage device 128. Additionally, the operating system and the software
can be run from a bootable medium, for example, a bootable CD, such as
KNOPPIX®, a bootable CD for GNU/Linux that is available as a
GNU/Linux distribution from knoppix.net.

[0087] Furthermore, the computing device 100 may include a network
interface 118 to interface to a Local Area Network (LAN), Wide Area
Network (WAN) or the Internet through a variety of connections including,
but not limited to, standard telephone lines, LAN or WAN links (e.g.,
802.11, T1, T3, 56 kb, X.25), broadband connections (e.g., ISDN, Frame
Relay, ATM), wireless connections, or some combination of any or all of
the above. The network interface 118 may comprise a built-in network
adapter, network interface card, PCMCIA network card, card bus network
adapter, wireless network adapter, USB network adapter, modem or any
other device suitable for interfacing the computing device 100 to any
type of network capable of communication and performing the operations
described herein. A wide variety of I/O devices 130a-130n may be present
in the computing device 100. Input devices include keyboards, mice,
trackpads, trackballs, microphones, and drawing tablets. Output devices
include video displays, speakers, inkjet printers, laser printers, and
dye-sublimation printers. The I/O devices 130 may be controlled by an I/O
controller 123 as shown in FIG. 1E. The I/O controller may control one or
more I/O devices such as a keyboard 126 and a pointing device 127, e.g.,
a mouse or optical pen. Furthermore, an I/O device may also provide
storage 128 and/or an installation medium 116 for the computing device
100. In still other embodiments, the computing device 100 may provide USB
connections to receive handheld USB storage devices such as the USB Flash
Drive line of devices manufactured by Twintech Industry, Inc. of Los
Alamitos, California.

[0088] In some embodiments, the computing device 100 may comprise or be
connected to multiple display devices 124a-124n, which each may be of the
same or different type and/or form. As such, any of the I/O devices
130a-130n and/or the I/O controller 123 may comprise any type and/or form
of suitable hardware, software, or combination of hardware and software
to support, enable or provide for the connection and use of multiple
display devices 124a-124n by the computing device 100. For example, the
computing device 100 may include any type and/or form of video adapter,
video card, driver, and/or library to interface, communicate, connect or
otherwise use the display devices 124a-124n. In one embodiment, a video
adapter may comprise multiple connectors to interface to multiple display
devices 124a-124n. In other embodiments, the computing device 100 may
include multiple video adapters, with each video adapter connected to one
or more of the display devices 124a-124n. In some embodiments, any
portion of the operating system of the computing device 100 may be
configured for using multiple displays 124a-124n. In other embodiments,
one or more of the display devices 124a-124n may be provided by one or
more other computing devices, such as computing devices 100a and 100b
connected to the computing device 100, for example, via a network. These
embodiments may include any type of software designed and constructed to
use another computer's display device as a second display device 124a for
the computing device 100. One ordinarily skilled in the art will
recognize and appreciate the various ways and embodiments that a
computing device 100 may be configured to have multiple display devices
124a-124n.

[0089] In further embodiments, an I/O device 130 may be a bridge 170
between the system bus 150 and an external communication bus, such as a
USB bus, an Apple Desktop Bus, an RS-232 serial connection, a SCSI bus, a
FireWire bus, a FireWire 800 bus, an Ethernet bus, an AppleTalk bus, a
Gigabit Ethernet bus, an Asynchronous Transfer Mode bus, a HIPPI bus, a
Super HIPPI bus, a SerialPlus bus, a SCI/LAMP bus, a FibreChannel bus, or
a Serial Attached small computer system interface bus.

[0090] A computing device 100 of the sort depicted in FIGS. 1E and 1F
typically operate under the control of operating systems, which control
scheduling of tasks and access to system resources. The computing device
100 can be running any operating system such as any of the versions of
the Microsoft® Windows operating systems, the different releases of
the Unix and Linux operating systems, any version of the Mac OS® for
Macintosh computers, any embedded operating system, any real-time
operating system, any open source operating system, any proprietary
operating system, any operating systems for mobile computing devices, or
any other operating system capable of running on the computing device and
performing the operations described herein. Typical operating systems
include: WINDOWS 3.x, WINDOWS 95, WINDOWS 98, WINDOWS 2000, WINDOWS NT
3.51, WINDOWS NT 4.0, WINDOWS CE, and WINDOWS XP, all of which are
manufactured by Microsoft Corporation of Redmond, Wash.; MacOS,
manufactured by Apple Computer of Cupertino, California; OS/2,
manufactured by International Business Machines of Armonk, N.Y.; and
Linux, a freely-available operating system distributed by Caldera Corp.
of Salt Lake City, Utah, or any type and/or form of a Unix operating
system, among others.

[0091] In other embodiments, the computing device 100 may have different
processors, operating systems, and input devices consistent with the
device. For example, in one embodiment the computer 100 is a Treo 180,
270, 1060, 600 or 650 smart phone manufactured by Palm, Inc. In this
embodiment, the Treo smart phone is operated under the control of the
PalmOS operating system and includes a stylus input device as well as a
five-way navigator device. Moreover, the computing device 100 can be any
workstation, desktop computer, laptop or notebook computer, server,
handheld computer, mobile telephone, any other computer, or other form of
computing or telecommunications device that is capable of communication
and that has sufficient processor power and memory capacity to perform
the operations described herein.

[0092] As shown in FIG. 1G, the computing device 100 may comprise multiple
processors and may provide functionality for simultaneous execution of
instructions or for simultaneous execution of one instruction on more
than one piece of data. In some embodiments, the computing device 100 may
comprise a parallel processor with one or more cores. In one of these
embodiments, the computing device 100 is a shared memory parallel device,
with multiple processors and/or multiple processor cores, accessing all
available memory as a single global address space. In another of these
embodiments, the computing device 100 is a distributed memory parallel
device with multiple processors each accessing local memory only. In
still another of these embodiments, the computing device 100 has both
some memory which is shared and some memory which can only be accessed by
particular processors or subsets of processors. In still even another of
these embodiments, the computing device 100, such as a multi-core
microprocessor, combines two or more independent processors into a single
package, often a single integrated circuit (IC). In yet another of these
embodiments, the computing device 100 includes a chip having a CELL
BROADBAND ENGINE architecture and including a Power processor element and
a plurality of synergistic processing elements, the Power processor
element and the plurality of synergistic processing elements linked
together by an internal high speed bus, which may be referred to as an
element interconnect bus.

[0093] In some embodiments, the processors provide functionality for
execution of a single instruction simultaneously on multiple pieces of
data (SIMD). In other embodiments, the processors provide functionality
for execution of multiple instructions simultaneously on multiple pieces
of data (MIMD). In still other embodiments, the processor may use any
combination of SIMD and MIMD cores in a single device.

[0094] In some embodiments, the computing device 100 may comprise a
graphics processing unit. In one of these embodiments, depicted in FIG.
1H, the computing device 100 includes at least one central processing
unit 101 and at least one graphics processing unit. In another of these
embodiments, the computing device 100 includes at least one parallel
processing unit and at least one graphics processing unit. In still
another of these embodiments, the computing device 100 includes a
plurality of processing units of any type, one of the plurality of
processing units comprising a graphics processing unit.

[0095] In some embodiments, a first computing device 100a executes an
application on behalf of a user of a client computing device 100b. In
other embodiments, a computing device 100a executes a virtual machine,
which provides an execution session within which applications execute on
behalf of a user or a client computing devices 100b. In one of these
embodiments, the execution session is a hosted desktop session. In
another of these embodiments, the computing device 100 executes a
terminal services session. The terminal services session may provide a
hosted desktop environment. In still another of these embodiments, the
execution session provides access to a computing environment, which may
comprise one or more of: an application, a plurality of applications, a
desktop application, and a desktop session in which one or more
applications may execute.

B. Appliance Architecture

[0096] FIG. 2A illustrates an example embodiment of the appliance 200. The
architecture of the appliance 200 in FIG. 2A is provided by way of
illustration only and is not intended to be limiting. As shown in FIG. 2,
appliance 200 comprises a hardware layer 206 and a software layer divided
into a user space 202 and a kernel space 204.

[0097] Hardware layer 206 provides the hardware elements upon which
programs and services within kernel space 204 and user space 202 are
executed. Hardware layer 206 also provides the structures and elements
which allow programs and services within kernel space 204 and user space
202 to communicate data both internally and externally with respect to
appliance 200. As shown in FIG. 2, the hardware layer 206 includes a
processing unit 262 for executing software programs and services, a
memory 264 for storing software and data, network ports 266 for
transmitting and receiving data over a network, and an encryption
processor 260 for performing functions related to Secure Sockets Layer
processing of data transmitted and received over the network. In some
embodiments, the central processing unit 262 may perform the functions of
the encryption processor 260 in a single processor. Additionally, the
hardware layer 206 may comprise multiple processors for each of the
processing unit 262 and the encryption processor 260. The processor 262
may include any of the processors 101 described above in connection with
FIGS. 1E and 1F. For example, in one embodiment, the appliance 200
comprises a first processor 262 and a second processor 262'. In other
embodiments, the processor 262 or 262' comprises a multi-core processor.

[0098] Although the hardware layer 206 of appliance 200 is generally
illustrated with an encryption processor 260, processor 260 may be a
processor for performing functions related to any encryption protocol,
such as the Secure Socket Layer (SSL) or Transport Layer Security (TLS)
protocol. In some embodiments, the processor 260 may be a general purpose
processor (GPP), and in further embodiments, may have executable
instructions for performing processing of any security related protocol.

[0099] Although the hardware layer 206 of appliance 200 is illustrated
with certain elements in FIG. 2, the hardware portions or components of
appliance 200 may comprise any type and form of elements, hardware or
software, of a computing device, such as the computing device 100
illustrated and discussed herein in conjunction with FIGS. 1E and 1F. In
some embodiments, the appliance 200 may comprise a server, gateway,
router, switch, bridge or other type of computing or network device, and
have any hardware and/or software elements associated therewith.

[0100] The operating system of appliance 200 allocates, manages, or
otherwise segregates the available system memory into kernel space 204
and user space 204. In example software architecture 200, the operating
system may be any type and/or form of Unix operating system although the
invention is not so limited. As such, the appliance 200 can be running
any operating system such as any of the versions of the Microsoft®
Windows operating systems, the different releases of the Unix and Linux
operating systems, any version of the Mac OS® for Macintosh
computers, any embedded operating system, any network operating system,
any real-time operating system, any open source operating system, any
proprietary operating system, any operating systems for mobile computing
devices or network devices, or any other operating system capable of
running on the appliance 200 and performing the operations described
herein.

[0101] The kernel space 204 is reserved for running the kernel 230,
including any device drivers, kernel extensions or other kernel related
software. As known to those skilled in the art, the kernel 230 is the
core of the operating system, and provides access, control, and
management of resources and hardware-related elements of the application
104. In accordance with an embodiment of the appliance 200, the kernel
space 204 also includes a number of network services or processes working
in conjunction with a cache manager 232, sometimes also referred to as
the integrated cache, the benefits of which are described in detail
further herein. Additionally, the embodiment of the kernel 230 will
depend on the embodiment of the operating system installed, configured,
or otherwise used by the device 200.

[0102] In one embodiment, the device 200 comprises one network stack 267,
such as a TCP/IP based stack, for communicating with the client 102
and/or the server 106. In one embodiment, the network stack 267 is used
to communicate with a first network, such as network 108, and a second
network 110. In some embodiments, the device 200 terminates a first
transport layer connection, such as a TCP connection of a client 102, and
establishes a second transport layer connection to a server 106 for use
by the client 102, e.g., the second transport layer connection is
terminated at the appliance 200 and the server 106. The first and second
transport layer connections may be established via a single network stack
267. In other embodiments, the device 200 may comprise multiple network
stacks, for example 267 and 267', and the first transport layer
connection may be established or terminated at one network stack 267, and
the second transport layer connection on the second network stack 267'.
For example, one network stack may be for receiving and transmitting
network packet on a first network, and another network stack for
receiving and transmitting network packets on a second network. In one
embodiment, the network stack 267 comprises a buffer 243 for queuing one
or more network packets for transmission by the appliance 200.

[0103] As shown in FIG. 2, the kernel space 204 includes the cache manager
232, a high-speed layer 2-7 integrated packet engine 240, an encryption
engine 234, a policy engine 236 and multi-protocol compression logic 238.
Running these components or processes 232, 240, 234, 236 and 238 in
kernel space 204 or kernel mode instead of the user space 202 improves
the performance of each of these components, alone and in combination.
Kernel operation means that these components or processes 232, 240, 234,
236 and 238 run in the core address space of the operating system of the
device 200. For example, running the encryption engine 234 in kernel mode
improves encryption performance by moving encryption and decryption
operations to the kernel, thereby reducing the number of transitions
between the memory space or a kernel thread in kernel mode and the memory
space or a thread in user mode. For example, data obtained in kernel mode
may not need to be passed or copied to a process or thread running in
user mode, such as from a kernel level data structure to a user level
data structure. In another aspect, the number of context switches between
kernel mode and user mode are also reduced. Additionally, synchronization
of and communications between any of the components or processes 232,
240, 235, 236 and 238 can be performed more efficiently in the kernel
space 204.

[0104] In some embodiments, any portion of the components 232, 240, 234,
236 and 238 may run or operate in the kernel space 204, while other
portions of these components 232, 240, 234, 236 and 238 may run or
operate in user space 202. In one embodiment, the appliance 200 uses a
kernel-level data structure providing access to any portion of one or
more network packets, for example, a network packet comprising a request
from a client 102 or a response from a server 106. In some embodiments,
the kernel-level data structure may be obtained by the packet engine 240
via a transport layer driver interface or filter to the network stack
267. The kernel-level data structure may comprise any interface and/or
data accessible via the kernel space 204 related to the network stack
267, network traffic or packets received or transmitted by the network
stack 267. In other embodiments, the kernel-level data structure may be
used by any of the components or processes 232, 240, 234, 236 and 238 to
perform the desired operation of the component or process. In one
embodiment, a component 232, 240, 234, 236 and 238 is running in kernel
mode 204 when using the kernel-level data structure, while in another
embodiment, the component 232, 240, 234, 236 and 238 is running in user
mode when using the kernel-level data structure. In some embodiments, the
kernel-level data structure may be copied or passed to a second
kernel-level data structure, or any desired user-level data structure.

[0105] The cache manager 232 may comprise software, hardware or any
combination of software and hardware to provide cache access, control and
management of any type and form of content, such as objects or
dynamically generated objects served by the originating servers 106. The
data, objects or content processed and stored by the cache manager 232
may comprise data in any format, such as a markup language, or
communicated via any protocol. In some embodiments, the cache manager 232
duplicates original data stored elsewhere or data previously computed,
generated or transmitted, in which the original data may require longer
access time to fetch, compute or otherwise obtain relative to reading a
cache memory element. Once the data is stored in the cache memory
element, future use can be made by accessing the cached copy rather than
refetching or recomputing the original data, thereby reducing the access
time. In some embodiments, the cache memory element may comprise a data
object in memory 264 of device 200. In other embodiments, the cache
memory element may comprise memory having a faster access time than
memory 264. In another embodiment, the cache memory element may comprise
any type and form of storage element of the device 200, such as a portion
of a hard disk. In some embodiments, the processing unit 262 may provide
cache memory for use by the cache manager 232. In yet further
embodiments, the cache manager 232 may use any portion and combination of
memory, storage, or the processing unit for caching data, objects, and
other content.

[0106] Furthermore, the cache manager 232 includes any logic, functions,
rules, or operations to perform any embodiments of the techniques of the
appliance 200 described herein. For example, the cache manager 232
includes logic or functionality to invalidate objects based on the
expiration of an invalidation time period or upon receipt of an
invalidation command from a client 102 or server 106. In some
embodiments, the cache manager 232 may operate as a program, service,
process or task executing in the kernel space 204, and in other
embodiments, in the user space 202. In one embodiment, a first portion of
the cache manager 232 executes in the user space 202 while a second
portion executes in the kernel space 204. In some embodiments, the cache
manager 232 can comprise any type of general purpose processor (GPP), or
any other type of integrated circuit, such as a Field Programmable Gate
Array (FPGA), Programmable Logic Device (PLD), or Application Specific
Integrated Circuit (ASIC).

[0107] The policy engine 236 may include, for example, an intelligent
statistical engine or other programmable application(s). In one
embodiment, the policy engine 236 provides a configuration mechanism to
allow a user to identify, specify, define or configure a caching policy.
Policy engine 236, in some embodiments, also has access to memory to
support data structures such as lookup tables or hash tables to enable
user-selected caching policy decisions. In other embodiments, the policy
engine 236 may comprise any logic, rules, functions or operations to
determine and provide access, control and management of objects, data or
content being cached by the appliance 200 in addition to access, control
and management of security, network traffic, network access, compression
or any other function or operation performed by the appliance 200.
Further examples of specific caching policies are further described
herein.

[0108] The encryption engine 234 comprises any logic, business rules,
functions or operations for handling the processing of any security
related protocol, such as SSL or TLS, or any function related thereto.
For example, the encryption engine 234 encrypts and decrypts network
packets, or any portion thereof, communicated via the appliance 200. The
encryption engine 234 may also setup or establish SSL or TLS connections
on behalf of the client 102a-102n, server 106a-106n, or appliance 200. As
such, the encryption engine 234 provides offloading and acceleration of
SSL processing. In one embodiment, the encryption engine 234 uses a
tunneling protocol to provide a virtual private network between a client
102a-102n and a server 106a-106n. In some embodiments, the encryption
engine 234 is in communication with the Encryption processor 260. In
other embodiments, the encryption engine 234 comprises executable
instructions running on the Encryption processor 260.

[0109] The multi-protocol compression engine 238 comprises any logic,
business rules, function or operations for compressing one or more
protocols of a network packet, such as any of the protocols used by the
network stack 267 of the device 200. In one embodiment, multi-protocol
compression engine 238 compresses bi-directionally between clients
102a-102n and servers 106a-106n any TCP/IP based protocol, including
Messaging Application Programming Interface (MAPI) (email), File Transfer
Protocol (FTP), HyperText Transfer Protocol (HTTP), Common Internet File
System (CIFS) protocol (file transfer), Independent Computing
Architecture (ICA) protocol, Remote Desktop Protocol (RDP), Wireless
Application Protocol (WAP), Mobile IP protocol, and Voice Over IP (VoIP)
protocol. In other embodiments, multi-protocol compression engine 238
provides compression of Hypertext Markup Language (HTML) based protocols
and in some embodiments, provides compression of any markup languages,
such as the Extensible Markup Language (XML). In one embodiment, the
multi-protocol compression engine 238 provides compression of any
high-performance protocol, such as any protocol designed for appliance
200 to appliance 200 communications. In another embodiment, the
multi-protocol compression engine 238 compresses any payload of or any
communication using a modified transport control protocol, such as
Transaction TCP (T/TCP), TCP with selection acknowledgements (TCP-SACK),
TCP with large windows (TCP-LW), a congestion prediction protocol such as
the TCP-Vegas protocol, and a TCP spoofing protocol.

[0110] As such, the multi-protocol compression engine 238 accelerates
performance for users accessing applications via desktop clients, e.g.,
Microsoft Outlook and non-Web thin clients, such as any client launched
by popular enterprise applications like Oracle, SAP and Siebel, and even
mobile clients, such as the Pocket PC. In some embodiments, the
multi-protocol compression engine 238 by executing in the kernel mode 204
and integrating with packet processing engine 240 accessing the network
stack 267 is able to compress any of the protocols carried by the TCP/IP
protocol, such as any application layer protocol.

[0111] High speed layer 2-7 integrated packet engine 240, also generally
referred to as a packet processing engine or packet engine, is
responsible for managing the kernel-level processing of packets received
and transmitted by appliance 200 via network ports 266. The high speed
layer 2-7 integrated packet engine 240 may comprise a buffer for queuing
one or more network packets during processing, such as for receipt of a
network packet or transmission of a network packet. Additionally, the
high speed layer 2-7 integrated packet engine 240 is in communication
with one or more network stacks 267 to send and receive network packets
via network ports 266. The high speed layer 2-7 integrated packet engine
240 works in conjunction with encryption engine 234, cache manager 232,
policy engine 236 and multi-protocol compression logic 238. In
particular, encryption engine 234 is configured to perform SSL processing
of packets, policy engine 236 is configured to perform functions related
to traffic management such as request-level content switching and
request-level cache redirection, and multi-protocol compression logic 238
is configured to perform functions related to compression and
decompression of data.

[0112] The high speed layer 2-7 integrated packet engine 240 includes a
packet processing timer 242. In one embodiment, the packet processing
timer 242 provides one or more time intervals to trigger the processing
of incoming, i.e., received, or outgoing, i.e., transmitted, network
packets. In some embodiments, the high speed layer 2-7 integrated packet
engine 240 processes network packets responsive to the timer 242. The
packet processing timer 242 provides any type and form of signal to the
packet engine 240 to notify, trigger, or communicate a time related
event, interval or occurrence. In many embodiments, the packet processing
timer 242 operates in the order of milliseconds, such as for example 100
ms, 50 ms or 25 ms. For example, in some embodiments, the packet
processing timer 242 provides time intervals or otherwise causes a
network packet to be processed by the high speed layer 2-7 integrated
packet engine 240 at a 10 ms time interval, while in other embodiments,
at a 5 ms time interval, and still yet in further embodiments, as short
as a 3, 2, or 1 ms time interval. The high speed layer 2-7 integrated
packet engine 240 may be interfaced, integrated or in communication with
the encryption engine 234, cache manager 232, policy engine 236 and
multi-protocol compression engine 238 during operation. As such, any of
the logic, functions, or operations of the encryption engine 234, cache
manager 232, policy engine 236 and multi-protocol compression logic 238
may be performed responsive to the packet processing timer 242 and/or the
packet engine 240. Therefore, any of the logic, functions, or operations
of the encryption engine 234, cache manager 232, policy engine 236 and
multi-protocol compression logic 238 may be performed at the granularity
of time intervals provided via the packet processing timer 242, for
example, at a time interval of less than or equal to 10 ms. For example,
in one embodiment, the cache manager 232 may perform invalidation of any
cached objects responsive to the high speed layer 2-7 integrated packet
engine 240 and/or the packet processing timer 242. In another embodiment,
the expiry or invalidation time of a cached object can be set to the same
order of granularity as the time interval of the packet processing timer
242, such as at every 10 ms.

[0113] In contrast to kernel space 204, user space 202 is the memory area
or portion of the operating system used by user mode applications or
programs otherwise running in user mode. A user mode application may not
access kernel space 204 directly and uses service calls in order to
access kernel services. As shown in FIG. 2, user space 202 of appliance
200 includes a graphical user interface (GUI) 210, a command line
interface (CLI) 212, shell services 214, health monitoring program 216,
and daemon services 218. GUI 210 and CLI 212 provide a means by which a
system administrator or other user can interact with and control the
operation of appliance 200, such as via the operating system of the
appliance 200. The GUI 210 or CLI 212 can comprise code running in user
space 202 or kernel space 204. The GUI 210 may be any type and form of
graphical user interface and may be presented via text, graphical or
otherwise, by any type of program or application, such as a browser. The
CLI 212 may be any type and form of command line or text-based interface,
such as a command line provided by the operating system. For example, the
CLI 212 may comprise a shell, which is a tool to enable users to interact
with the operating system. In some embodiments, the CLI 212 may be
provided via a bash, csh, tcsh, or ksh type shell. The shell services 214
comprises the programs, services, tasks, processes or executable
instructions to support interaction with the appliance 200 or operating
system by a user via the GUI 210 and/or CLI 212.

[0114] Health monitoring program 216 is used to monitor, check, report and
ensure that network systems are functioning properly and that users are
receiving requested content over a network. Health monitoring program 216
comprises one or more programs, services, tasks, processes or executable
instructions to provide logic, rules, functions or operations for
monitoring any activity of the appliance 200. In some embodiments, the
health monitoring program 216 intercepts and inspects any network traffic
passed via the appliance 200. In other embodiments, the health monitoring
program 216 interfaces by any suitable means and/or mechanisms with one
or more of the following: the encryption engine 234, cache manager 232,
policy engine 236, multi-protocol compression logic 238, packet engine
240, daemon services 218, and shell services 214. As such, the health
monitoring program 216 may call any application programming interface
(API) to determine a state, status, or health of any portion of the
appliance 200. For example, the health monitoring program 216 may ping or
send a status inquiry on a periodic basis to check if a program, process,
service or task is active and currently running. In another example, the
health monitoring program 216 may check any status, error or history logs
provided by any program, process, service or task to determine any
condition, status or error with any portion of the appliance 200.

[0115] Daemon services 218 are programs that run continuously or in the
background and handle periodic service requests received by appliance
200. In some embodiments, a daemon service may forward the requests to
other programs or processes, such as another daemon service 218 as
appropriate. As known to those skilled in the art, a daemon service 218
may run unattended to perform continuous or periodic system wide
functions, such as network control, or to perform any desired task. In
some embodiments, one or more daemon services 218 run in the user space
202, while in other embodiments, one or more daemon services 218 run in
the kernel space.

[0116] Referring now to FIG. 2B, another embodiment of the appliance 200
is depicted. In brief overview, the appliance 200 provides one or more of
the following services, functionality or operations: SSL VPN connectivity
280, switching/load balancing 284, Domain Name Service resolution 286,
acceleration 288 and an application firewall 290 for communications
between one or more clients 102 and one or more servers 106. Each of the
servers 106 may provide one or more network related services 270a-270n
(referred to as services 270). For example, a server 106 may provide an
http service 270. The appliance 200 comprises one or more virtual servers
or virtual internet protocol servers, referred to as a vServer, VIP
server, or just VIP 275a-275n (also referred herein as vServer 275). The
vServer 275 receives, intercepts or otherwise processes communications
between a client 102 and a server 106 in accordance with the
configuration and operations of the appliance 200.

[0117] The vServer 275 may comprise software, hardware or any combination
of software and hardware. The vServer 275 may comprise any type and form
of program, service, task, process or executable instructions operating
in user mode 202, kernel mode 204 or any combination thereof in the
appliance 200. The vServer 275 includes any logic, functions, rules, or
operations to perform any embodiments of the techniques described herein,
such as SSL VPN 280, switching/load balancing 284, Domain Name Service
resolution 286, acceleration 288 and an application firewall 290. In some
embodiments, the vServer 275 establishes a connection to a service 270 of
a server 106. The service 275 may comprise any program, application,
process, task or set of executable instructions capable of connecting to
and communicating to the appliance 200, client 102 or vServer 275. For
example, the service 275 may comprise a web server, http server, ftp,
email or database server. In some embodiments, the service 270 is a
daemon process or network driver for listening, receiving and/or sending
communications for an application, such as email, database or an
enterprise application. In some embodiments, the service 270 may
communicate on a specific IP address, or IP address and port.

[0118] In some embodiments, the vServer 275 applies one or more policies
of the policy engine 236 to network communications between the client 102
and server 106. In one embodiment, the policies are associated with a
vServer 275. In another embodiment, the policies are based on a user, or
a group of users. In yet another embodiment, a policy is global and
applies to one or more vServers 275a-275n, and any user or group of users
communicating via the appliance 200. In some embodiments, the policies of
the policy engine have conditions upon which the policy is applied based
on any content of the communication, such as internet protocol address,
port, protocol type, header or fields in a packet, or the context of the
communication, such as user, group of the user, vServer 275, transport
layer connection, and/or identification or attributes of the client 102
or server 106.

[0119] In other embodiments, the appliance 200 communicates or interfaces
with the policy engine 236 to determine authentication and/or
authorization of a remote user or a remote client 102 to access the
computing environment 15, application, and/or data file from a server
106. In another embodiment, the appliance 200 communicates or interfaces
with the policy engine 236 to determine authentication and/or
authorization of a remote user or a remote client 102 to have the
application delivery system 190 deliver one or more of the computing
environment 15, application, and/or data file. In yet another embodiment,
the appliance 200 establishes a VPN or SSL VPN connection based on the
policy engine's 236 authentication and/or authorization of a remote user
or a remote client 102 In one embodiment, the appliance 200 controls the
flow of network traffic and communication sessions based on policies of
the policy engine 236. For example, the appliance 200 may control the
access to a computing environment 15, application or data file based on
the policy engine 236.

[0120] In some embodiments, the vServer 275 establishes a transport layer
connection, such as a TCP or UDP connection with a client 102 via the
client agent 120. In one embodiment, the vServer 275 listens for and
receives communications from the client 102. In other embodiments, the
vServer 275 establishes a transport layer connection, such as a TCP or
UDP connection with a client server 106. In one embodiment, the vServer
275 establishes the transport layer connection to an internet protocol
address and port of a server 270 running on the server 106. In another
embodiment, the vServer 275 associates a first transport layer connection
to a client 102 with a second transport layer connection to the server
106. In some embodiments, a vServer 275 establishes a pool of transport
layer connections to a server 106 and multiplexes client requests via the
pooled transport layer connections.

[0121] In some embodiments, the appliance 200 provides a SSL VPN
connection 280 between a client 102 and a server 106. For example, a
client 102 on a first network 102 requests to establish a connection to a
server 106 on a second network 104'. In some embodiments, the second
network 104' is not routable from the first network 104. In other
embodiments, the client 102 is on a public network 104 and the server 106
is on a private network 104', such as a corporate network. In one
embodiment, the client agent 120 intercepts communications of the client
102 on the first network 104, encrypts the communications, and transmits
the communications via a first transport layer connection to the
appliance 200. The appliance 200 associates the first transport layer
connection on the first network 104 to a second transport layer
connection to the server 106 on the second network 104. The appliance 200
receives the intercepted communication from the client agent 102,
decrypts the communications, and transmits the communication to the
server 106 on the second network 104 via the second transport layer
connection. The second transport layer connection may be a pooled
transport layer connection. As such, the appliance 200 provides an
end-to-end secure transport layer connection for the client 102 between
the two networks 104, 104'.

[0122] In one embodiment, the appliance 200 hosts an intranet internet
protocol or IntranetIP 282 address of the client 102 on the virtual
private network 104. The client 102 has a local network identifier, such
as an internet protocol (IP) address and/or host name on the first
network 104. When connected to the second network 104' via the appliance
200, the appliance 200 establishes, assigns or otherwise provides an
IntranetIP address 282, which is a network identifier, such as IP address
and/or host name, for the client 102 on the second network 104'. The
appliance 200 listens for and receives on the second or private network
104' for any communications directed towards the client 102 using the
client's established IntranetIP 282. In one embodiment, the appliance 200
acts as or on behalf of the client 102 on the second private network 104.
For example, in another embodiment, a vServer 275 listens for and
responds to communications to the IntranetIP 282 of the client 102. In
some embodiments, if a computing device 100 on the second network 104'
transmits a request, the appliance 200 processes the request as if it
were the client 102. For example, the appliance 200 may respond to a ping
to the client's IntranetIP 282. In another example, the appliance may
establish a connection, such as a TCP or UDP connection, with computing
device 100 on the second network 104 requesting a connection with the
client's IntranetIP 282.

[0123] In some embodiments, the appliance 200 provides one or more of the
following acceleration techniques 288 to communications between the
client 102 and server 106: 1) compression; 2) decompression; 3)
Transmission Control Protocol pooling; 4) Transmission Control Protocol
multiplexing; 5) Transmission Control Protocol buffering; and 6) caching.
In one embodiment, the appliance 200 relieves servers 106 of much of the
processing load caused by repeatedly opening and closing transport layers
connections to clients 102 by opening one or more transport layer
connections with each server 106 and maintaining these connections to
allow repeated data accesses by clients via the Internet. This technique
is referred to herein as "connection pooling".

[0124] In some embodiments, in order to seamlessly splice communications
from a client 102 to a server 106 via a pooled transport layer
connection, the appliance 200 translates or multiplexes communications by
modifying sequence number and acknowledgment numbers at the transport
layer protocol level. This is referred to as "connection multiplexing".
In some embodiments, no application layer protocol interaction is
required. For example, in the case of an in-bound packet (that is, a
packet received from a client 102), the source network address of the
packet is changed to that of an output port of appliance 200, and the
destination network address is changed to that of the intended server. In
the case of an outbound packet (that is, one received from a server 106),
the source network address is changed from that of the server 106 to that
of an output port of appliance 200 and the destination address is changed
from that of appliance 200 to that of the requesting client 102. The
sequence numbers and acknowledgment numbers of the packet are also
translated to sequence numbers and acknowledgement numbers expected by
the client 102 on the appliance's 200 transport layer connection to the
client 102. In some embodiments, the packet checksum of the transport
layer protocol is recalculated to account for these translations.

[0125] In another embodiment, the appliance 200 provides switching or
load-balancing functionality 284 for communications between the client
102 and server 106. In some embodiments, the appliance 200 distributes
traffic and directs client requests to a server 106 based on layer 4 or
application-layer request data. In one embodiment, although the network
layer or layer 2 of the network packet identifies a destination server
106, the appliance 200 determines the server 106 to distribute the
network packet by application information and data carried as payload of
the transport layer packet. In one embodiment, the health monitoring
programs 216 of the appliance 200 monitor the health of servers to
determine the server 106 for which to distribute a client's request. In
some embodiments, if the appliance 200 detects a server 106 is not
available or has a load over a predetermined threshold, the appliance 200
can direct or distribute client requests to another server 106.

[0126] In some embodiments, the appliance 200 acts as a Domain Name
Service (DNS) resolver or otherwise provides resolution of a DNS request
from clients 102. In some embodiments, the appliance intercepts a DNS
request transmitted by the client 102. In one embodiment, the appliance
200 responds to a client's DNS request with an IP address of or hosted by
the appliance 200. In this embodiment, the client 102 transmits network
communication for the domain name to the appliance 200. In another
embodiment, the appliance 200 responds to a client's DNS request with an
IP address of or hosted by a second appliance 200'. In some embodiments,
the appliance 200 responds to a client's DNS request with an IP address
of a server 106 determined by the appliance 200.

[0127] In yet another embodiment, the appliance 200 provides application
firewall functionality 290 for communications between the client 102 and
server 106. In one embodiment, the policy engine 236 provides rules for
detecting and blocking illegitimate requests. In some embodiments, the
application firewall 290 protects against denial of service (DoS)
attacks. In other embodiments, the appliance inspects the content of
intercepted requests to identify and block application-based attacks. In
some embodiments, the rules/policy engine 236 comprises one or more
application firewall or security control policies for providing
protections against various classes and types of web or Internet based
vulnerabilities, such as one or more of the following: 1) buffer
overflow, 2) CGI-BIN parameter manipulation, 3) form/hidden field
manipulation, 4) forceful browsing, 5) cookie or session poisoning, 6)
broken access control list (ACLs) or weak passwords, 7) cross-site
scripting (XSS), 8) command injection, 9) SQL injection, 10) error
triggering sensitive information leak, 11) insecure use of cryptography,
12) server misconfiguration, 13) back doors and debug options, 14)
website defacement, 15) platform or operating systems vulnerabilities,
and 16) zero-day exploits. In an embodiment, the application firewall 290
provides HTML form field protection in the form of inspecting or
analyzing the network communication for one or more of the following: 1)
required fields are returned, 2) no added field allowed, 3) read-only and
hidden field enforcement, 4) drop-down list and radio button field
conformance, and 5) form-field max-length enforcement. In some
embodiments, the application firewall 290 ensures cookies are not
modified. In other embodiments, the application firewall 290 protects
against forceful browsing by enforcing legal URLs.

[0128] In still yet other embodiments, the application firewall 290
protects any confidential information contained in the network
communication. The application firewall 290 may inspect or analyze any
network communication in accordance with the rules or polices of the
engine 236 to identify any confidential information in any field of the
network packet. In some embodiments, the application firewall 290
identifies in the network communication one or more occurrences of a
credit card number, password, social security number, name, patient code,
contact information, and age. The encoded portion of the network
communication may comprise these occurrences or the confidential
information. Based on these occurrences, in one embodiment, the
application firewall 290 may take a policy action on the network
communication, such as prevent transmission of the network communication.
In another embodiment, the application firewall 290 may rewrite, remove
or otherwise mask such identified occurrence or confidential information.

[0129] Still referring to FIG. 2B, the appliance 200 may include a
performance monitoring agent 197 as discussed above in conjunction with
FIG. 1D. In one embodiment, the appliance 200 receives the monitoring
agent 197 from the monitoring service 198 or monitoring server 106 as
depicted in FIG. 1D. In some embodiments, the appliance 200 stores the
monitoring agent 197 in storage, such as disk, for delivery to any client
or server in communication with the appliance 200. For example, in one
embodiment, the appliance 200 transmits the monitoring agent 197 to a
client upon receiving a request to establish a transport layer
connection. In other embodiments, the appliance 200 transmits the
monitoring agent 197 upon establishing the transport layer connection
with the client 102. In another embodiment, the appliance 200 transmits
the monitoring agent 197 to the client upon intercepting or detecting a
request for a web page. In yet another embodiment, the appliance 200
transmits the monitoring agent 197 to a client or a server in response to
a request from the monitoring server 198. In one embodiment, the
appliance 200 transmits the monitoring agent 197 to a second appliance
200' or appliance 205.

[0130] In other embodiments, the appliance 200 executes the monitoring
agent 197. In one embodiment, the monitoring agent 197 measures and
monitors the performance of any application, program, process, service,
task or thread executing on the appliance 200. For example, the
monitoring agent 197 may monitor and measure performance and operation of
vServers 275A-275N. In another embodiment, the monitoring agent 197
measures and monitors the performance of any transport layer connections
of the appliance 200. In some embodiments, the monitoring agent 197
measures and monitors the performance of any user sessions traversing the
appliance 200. In one embodiment, the monitoring agent 197 measures and
monitors the performance of any virtual private network connections
and/or sessions traversing the appliance 200, such an SSL VPN session. In
still further embodiments, the monitoring agent 197 measures and monitors
the memory, CPU and disk usage and performance of the appliance 200. In
yet another embodiment, the monitoring agent 197 measures and monitors
the performance of any acceleration technique 288 performed by the
appliance 200, such as SSL offloading, connection pooling and
multiplexing, caching, and compression. In some embodiments, the
monitoring agent 197 measures and monitors the performance of any load
balancing and/or content switching 284 performed by the appliance 200. In
other embodiments, the monitoring agent 197 measures and monitors the
performance of application firewall 290 protection and processing
performed by the appliance 200.

C. Client Agent

[0131] Referring now to FIG. 3, an embodiment of the client agent 120 is
depicted. The client 102 includes a client agent 120 for establishing and
exchanging communications with the appliance 200 and/or server 106 via a
network 104. In brief overview, the client 102 operates on computing
device 100 having an operating system with a kernel mode 302 and a user
mode 303, and a network stack 310 with one or more layers 310a-310b. The
client 102 may have installed and/or execute one or more applications. In
some embodiments, one or more applications may communicate via the
network stack 310 to a network 104. One of the applications, such as a
web browser, may also include a first program 322. For example, the first
program 322 may be used in some embodiments to install and/or execute the
client agent 120, or any portion thereof. The client agent 120 includes
an interception mechanism, or interceptor 350, for intercepting network
communications from the network stack 310 from the one or more
applications.

[0132] The network stack 310 of the client 102 may comprise any type and
form of software, or hardware, or any combinations thereof, for providing
connectivity to and communications with a network. In one embodiment, the
network stack 310 comprises a software implementation for a network
protocol suite. The network stack 310 may comprise one or more network
layers, such as any networks layers of the Open Systems Interconnection
(OSI) communications model as those skilled in the art recognize and
appreciate. As such, the network stack 310 may comprise any type and form
of protocols for any of the following layers of the OSI model: 1)
physical link layer, 2) data link layer, 3) network layer, 4) transport
layer, 5) session layer, 6) presentation layer, and 7) application layer.
In one embodiment, the network stack 310 may comprise a transport control
protocol (TCP) over the network layer protocol of the internet protocol
(IP), generally referred to as TCP/IP. In some embodiments, the TCP/IP
protocol may be carried over the Ethernet protocol, which may comprise
any of the family of IEEE wide-area-network (WAN) or local-area-network
(LAN) protocols, such as those protocols covered by the IEEE 802.3. In
some embodiments, the network stack 310 comprises any type and form of a
wireless protocol, such as IEEE 802.11 and/or mobile internet protocol.

[0133] In view of a TCP/IP based network, any TCP/IP based protocol may be
used, including Messaging Application Programming Interface (MAPI)
(email), File Transfer Protocol (FTP), HyperText Transfer Protocol
(HTTP), Common Internet File System (CIFS) protocol (file transfer),
Independent Computing Architecture (ICA) protocol, Remote Desktop
Protocol (RDP), Wireless Application Protocol (WAP), Mobile IP protocol,
and Voice Over IP (VoIP) protocol. In another embodiment, the network
stack 310 comprises any type and form of transport control protocol, such
as a modified transport control protocol, for example a Transaction TCP
(T/TCP), TCP with selection acknowledgements (TCP-SACK), TCP with large
windows (TCP-LW), a congestion prediction protocol such as the TCP-Vegas
protocol, and a TCP spoofing protocol. In other embodiments, any type and
form of user datagram protocol (UDP), such as UDP over IP, may be used by
the network stack 310, such as for voice communications or real-time data
communications.

[0134] Furthermore, the network stack 310 may include one or more network
drivers supporting the one or more layers, such as a TCP driver or a
network layer driver. The network drivers may be included as part of the
operating system of the computing device 100 or as part of any network
interface cards or other network access components of the computing
device 100. In some embodiments, any of the network drivers of the
network stack 310 may be customized, modified or adapted to provide a
custom or modified portion of the network stack 310 in support of any of
the techniques described herein. In other embodiments, the acceleration
program 302 is designed and constructed to operate with or work in
conjunction with the network stack 310 installed or otherwise provided by
the operating system of the client 102.

[0135] The network stack 310 comprises any type and form of interfaces for
receiving, obtaining, providing or otherwise accessing any information
and data related to network communications of the client 102. In one
embodiment, an interface to the network stack 310 comprises an
application programming interface (API). The interface may also comprise
any function call, hooking or filtering mechanism, event or call back
mechanism, or any type of interfacing technique. The network stack 310
via the interface may receive or provide any type and form of data
structure, such as an object, related to functionality or operation of
the network stack 310. For example, the data structure may comprise
information and data related to a network packet or one or more network
packets. In some embodiments, the data structure comprises a portion of
the network packet processed at a protocol layer of the network stack
310, such as a network packet of the transport layer. In some
embodiments, the data structure 325 comprises a kernel-level data
structure, while in other embodiments, the data structure 325 comprises a
user-mode data structure. A kernel-level data structure may comprise a
data structure obtained or related to a portion of the network stack 310
operating in kernel-mode 302, or a network driver or other software
running in kernel-mode 302, or any data structure obtained or received by
a service, process, task, thread or other executable instructions running
or operating in kernel-mode of the operating system.

[0136] Additionally, some portions of the network stack 310 may execute or
operate in kernel-mode 302, for example, the data link or network layer,
while other portions execute or operate in user-mode 303, such as an
application layer of the network stack 310. For example, a first portion
310a of the network stack may provide user-mode access to the network
stack 310 to an application while a second portion 310a of the network
stack 310 provides access to a network. In some embodiments, a first
portion 310a of the network stack may comprise one or more upper layers
of the network stack 310, such as any of layers 5-7. In other
embodiments, a second portion 310b of the network stack 310 comprises one
or more lower layers, such as any of layers 1-4. Each of the first
portion 310a and second portion 310b of the network stack 310 may
comprise any portion of the network stack 310, at any one or more network
layers, in user-mode 203, kernel-mode, 202, or combinations thereof, or
at any portion of a network layer or interface point to a network layer
or any portion of or interface point to the user-mode 203 and kernel-mode
203.

[0137] The interceptor 350 may comprise software, hardware, or any
combination of software and hardware. In one embodiment, the interceptor
350 intercept a network communication at any point in the network stack
310, and redirects or transmits the network communication to a
destination desired, managed or controlled by the interceptor 350 or
client agent 120. For example, the interceptor 350 may intercept a
network communication of a network stack 310 of a first network and
transmit the network communication to the appliance 200 for transmission
on a second network 104. In some embodiments, the interceptor 350
comprises any type interceptor 350 comprises a driver, such as a network
driver constructed and designed to interface and work with the network
stack 310. In some embodiments, the client agent 120 and/or interceptor
350 operates at one or more layers of the network stack 310, such as at
the transport layer. In one embodiment, the interceptor 350 comprises a
filter driver, hooking mechanism, or any form and type of suitable
network driver interface that interfaces to the transport layer of the
network stack, such as via the transport driver interface (TDI). In some
embodiments, the interceptor 350 interfaces to a first protocol layer,
such as the transport layer and another protocol layer, such as any layer
above the transport protocol layer, for example, an application protocol
layer. In one embodiment, the interceptor 350 may comprise a driver
complying with the Network Driver Interface Specification (NDIS), or a
NDIS driver. In another embodiment, the interceptor 350 may comprise a
mini-filter or a mini-port driver. In one embodiment, the interceptor
350, or portion thereof, operates in kernel-mode 202. In another
embodiment, the interceptor 350, or portion thereof, operates in
user-mode 203. In some embodiments, a portion of the interceptor 350
operates in kernel-mode 202 while another portion of the interceptor 350
operates in user-mode 203. In other embodiments, the client agent 120
operates in user-mode 203 but interfaces via the interceptor 350 to a
kernel-mode driver, process, service, task or portion of the operating
system, such as to obtain a kernel-level data structure 225. In further
embodiments, the interceptor 350 is a user-mode application or program,
such as application.

[0138] In one embodiment, the interceptor 350 intercepts any transport
layer connection requests. In these embodiments, the interceptor 350
execute transport layer application programming interface (API) calls to
set the destination information, such as destination IP address and/or
port to a desired location for the location. In this manner, the
interceptor 350 intercepts and redirects the transport layer connection
to a IP address and port controlled or managed by the interceptor 350 or
client agent 120. In one embodiment, the interceptor 350 sets the
destination information for the connection to a local IP address and port
of the client 102 on which the client agent 120 is listening. For
example, the client agent 120 may comprise a proxy service listening on a
local IP address and port for redirected transport layer communications.
In some embodiments, the client agent 120 then communicates the
redirected transport layer communication to the appliance 200.

[0139] In some embodiments, the interceptor 350 intercepts a Domain Name
Service (DNS) request. In one embodiment, the client agent 120 and/or
interceptor 350 resolves the DNS request. In another embodiment, the
interceptor transmits the intercepted DNS request to the appliance 200
for DNS resolution. In one embodiment, the appliance 200 resolves the DNS
request and communicates the DNS response to the client agent 120. In
some embodiments, the appliance 200 resolves the DNS request via another
appliance 200' or a DNS server 106.

[0140] In yet another embodiment, the client agent 120 may comprise two
agents 120 and 120'. In one embodiment, a first agent 120 may comprise an
interceptor 350 operating at the network layer of the network stack 310.
In some embodiments, the first agent 120 intercepts network layer
requests such as Internet Control Message Protocol (ICMP) requests (e.g.,
ping and traceroute). In other embodiments, the second agent 120' may
operate at the transport layer and intercept transport layer
communications. In some embodiments, the first agent 120 intercepts
communications at one layer of the network stack 210 and interfaces with
or communicates the intercepted communication to the second agent 120'.

[0141] The client agent 120 and/or interceptor 350 may operate at or
interface with a protocol layer in a manner transparent to any other
protocol layer of the network stack 310. For example, in one embodiment,
the interceptor 350 operates or interfaces with the transport layer of
the network stack 310 transparently to any protocol layer below the
transport layer, such as the network layer, and any protocol layer above
the transport layer, such as the session, presentation or application
layer protocols. This allows the other protocol layers of the network
stack 310 to operate as desired and without modification for using the
interceptor 350. As such, the client agent 120 and/or interceptor 350 can
interface with the transport layer to secure, optimize, accelerate, route
or load-balance any communications provided via any protocol carried by
the transport layer, such as any application layer protocol over TCP/IP.

[0142] Furthermore, the client agent 120 and/or interceptor may operate at
or interface with the network stack 310 in a manner transparent to any
application, a user of the client 102, and any other computing device,
such as a server, in communications with the client 102. The client agent
120 and/or interceptor 350 may be installed and/or executed on the client
102 in a manner without modification of an application. In some
embodiments, the user of the client 102 or a computing device in
communications with the client 102 are not aware of the existence,
execution or operation of the client agent 120 and/or interceptor 350. As
such, in some embodiments, the client agent 120 and/or interceptor 350 is
installed, executed, and/or operated transparently to an application,
user of the client 102, another computing device, such as a server, or
any of the protocol layers above and/or below the protocol layer
interfaced to by the interceptor 350.

[0143] The client agent 120 includes an acceleration program 302, a
streaming client 306, a collection agent 304, and/or monitoring agent
197. In one embodiment, the client agent 120 comprises an Independent
Computing Architecture (ICA) client, or any portion thereof, developed by
Citrix Systems, Inc. of Fort Lauderdale, Fla., and is also referred to as
an ICA client. In some embodiments, the client 120 comprises an
application streaming client 306 for streaming an application from a
server 106 to a client 102. In some embodiments, the client agent 120
comprises an acceleration program 302 for accelerating communications
between client 102 and server 106. In another embodiment, the client
agent 120 includes a collection agent 304 for performing end-point
detection/scanning and collecting end-point information for the appliance
200 and/or server 106.

[0144] In some embodiments, the acceleration program 302 comprises a
client-side acceleration program for performing one or more acceleration
techniques to accelerate, enhance or otherwise improve a client's
communications with and/or access to a server 106, such as accessing an
application provided by a server 106. The logic, functions, and/or
operations of the executable instructions of the acceleration program 302
may perform one or more of the following acceleration techniques: 1)
multi-protocol compression, 2) transport control protocol pooling, 3)
transport control protocol multiplexing, 4) transport control protocol
buffering, and 5) caching via a cache manager. Additionally, the
acceleration program 302 may perform encryption and/or decryption of any
communications received and/or transmitted by the client 102. In some
embodiments, the acceleration program 302 performs one or more of the
acceleration techniques in an integrated manner or fashion. Additionally,
the acceleration program 302 can perform compression on any of the
protocols, or multiple-protocols, carried as a payload of a network
packet of the transport layer protocol.

[0145] The streaming client 306 comprises an application, program,
process, service, task or executable instructions for receiving and
executing a streamed application from a server 106. A server 106 may
stream one or more application data files to the streaming client 306 for
playing, executing or otherwise causing to be executed the application on
the client 102. In some embodiments, the server 106 transmits a set of
compressed or packaged application data files to the streaming client
306. In some embodiments, the plurality of application files are
compressed and stored on a file server within an archive file such as a
CAB, ZIP, SIT, TAR, JAR or other archive. In one embodiment, the server
106 decompresses, unpackages or unarchives the application files and
transmits the files to the client 102. In another embodiment, the client
102 decompresses, unpackages or unarchives the application files. The
streaming client 306 dynamically installs the application, or portion
thereof, and executes the application. In one embodiment, the streaming
client 306 may be an executable program. In some embodiments, the
streaming client 306 may be able to launch another executable program.

[0146] The collection agent 304 comprises an application, program,
process, service, task or executable instructions for identifying,
obtaining and/or collecting information about the client 102. In some
embodiments, the appliance 200 transmits the collection agent 304 to the
client 102 or client agent 120. The collection agent 304 may be
configured according to one or more policies of the policy engine 236 of
the appliance. In other embodiments, the collection agent 304 transmits
collected information on the client 102 to the appliance 200. In one
embodiment, the policy engine 236 of the appliance 200 uses the collected
information to determine and provide access, authentication and
authorization control of the client's connection to a network 104.

[0147] In one embodiment, the collection agent 304 comprises an end-point
detection and scanning mechanism, which identifies and determines one or
more attributes or characteristics of the client. For example, the
collection agent 304 may identify and determine any one or more of the
following client-side attributes: 1) the operating system an/or a version
of an operating system, 2) a service pack of the operating system, 3) a
running service, 4) a running process, and 5) a file. The collection
agent 304 may also identify and determine the presence or versions of any
one or more of the following on the client: 1) antivirus software, 2)
personal firewall software, 3) anti-spam software, and 4) internet
security software. The policy engine 236 may have one or more policies
based on any one or more of the attributes or characteristics of the
client or client-side attributes.

[0148] In some embodiments, the client agent 120 includes a monitoring
agent 197 as discussed in conjunction with FIGS. 1D and 2B. The
monitoring agent 197 may be any type and form of script, such as Visual
Basic or Java script. In one embodiment, the monitoring agent 197
monitors and measures performance of any portion of the client agent 120.
For example, in some embodiments, the monitoring agent 197 monitors and
measures performance of the acceleration program 302. In another
embodiment, the monitoring agent 197 monitors and measures performance of
the streaming client 306. In other embodiments, the monitoring agent 197
monitors and measures performance of the collection agent 304. In still
another embodiment, the monitoring agent 197 monitors and measures
performance of the interceptor 350. In some embodiments, the monitoring
agent 197 monitors and measures any resource of the client 102, such as
memory, CPU and disk.

[0149] The monitoring agent 197 may monitor and measure performance of any
application of the client. In one embodiment, the monitoring agent 197
monitors and measures performance of a browser on the client 102. In some
embodiments, the monitoring agent 197 monitors and measures performance
of any application delivered via the client agent 120. In other
embodiments, the monitoring agent 197 measures and monitors end user
response times for an application, such as web-based or HTTP response
times. The monitoring agent 197 may monitor and measure performance of an
ICA or RDP client. In another embodiment, the monitoring agent 197
measures and monitors metrics for a user session or application session.
In some embodiments, monitoring agent 197 measures and monitors an ICA or
RDP session. In one embodiment, the monitoring agent 197 measures and
monitors the performance of the appliance 200 in accelerating delivery of
an application and/or data to the client 102.

[0150] In some embodiments and still referring to FIG. 3, a first program
322 may be used to install and/or execute the client agent 120, or
portion thereof, such as the interceptor 350, automatically, silently,
transparently, or otherwise. In one embodiment, the first program 322
comprises a plugin component, such an ActiveX control or Java control or
script that is loaded into and executed by an application. For example,
the first program comprises an ActiveX control loaded and run by a web
browser application, such as in the memory space or context of the
application. In another embodiment, the first program 322 comprises a set
of executable instructions loaded into and run by the application, such
as a browser. In one embodiment, the first program 322 comprises a
designed and constructed program to install the client agent 120. In some
embodiments, the first program 322 obtains, downloads, or receives the
client agent 120 via the network from another computing device. In
another embodiment, the first program 322 is an installer program or a
plug and play manager for installing programs, such as network drivers,
on the operating system of the client 102.

[0151] Referring now to FIG. 4A, a block diagram depicts one embodiment of
a virtualization environment 400. In brief overview, a computing device
100 includes a hypervisor layer, a virtualization layer, and a hardware
layer. The hypervisor layer includes a hypervisor 401 (also referred to
as a virtualization manager) that allocates and manages access to a
number of physical resources in the hardware layer (e.g., the
processor(s) 421, and disk(s) 428) by at least one virtual machine
executing in the virtualization layer. The virtualization layer includes
at least one operating system 410 and a plurality of virtual resources
allocated to the at least one operating system 410. Virtual resources may
include, without limitation, a plurality of virtual processors 432a,
432b, 432c (generally 432), and virtual disks 442a, 442b, 442c (generally
442), as well as virtual resources such as virtual memory and virtual
network interfaces. The plurality of virtual resources and the operating
system 410 may be referred to as a virtual machine 406. A virtual machine
406 may include a control operating system 405 in communication with the
hypervisor 401 and used to execute applications for managing and
configuring other virtual machines on the computing device 100.

[0152] In greater detail, a hypervisor 401 may provide virtual resources
to an operating system in any manner which simulates the operating system
having access to a physical device. A hypervisor 401 may provide virtual
resources to any number of guest operating systems 410a, 410b (generally
410). In some embodiments, a computing device 100 executes one or more
types of hypervisors. In these embodiments, hypervisors may be used to
emulate virtual hardware, partition physical hardware, virtualize
physical hardware, and execute virtual machines that provide access to
computing environments. Hypervisors may include those manufactured by
VMWare, Inc., of Palo Alto, Calif.; the XEN hypervisor, an open source
product whose development is overseen by the open source Xen.org
community; HyperV, VirtualServer or virtual PC hypervisors provided by
Microsoft, or others. In some embodiments, a computing device 100
executing a hypervisor that creates a virtual machine platform on which
guest operating systems may execute is referred to as a host server. In
one of these embodiments, for example, the computing device 100 is a XEN
SERVER provided by Citrix Systems, Inc., of Fort Lauderdale, Fla.

[0153] In some embodiments, a hypervisor 401 executes within an operating
system executing on a computing device. In one of these embodiments, a
computing device executing an operating system and a hypervisor 401 may
be said to have a host operating system (the operating system executing
on the computing device), and a guest operating system (an operating
system executing within a computing resource partition provided by the
hypervisor 401). In other embodiments, a hypervisor 401 interacts
directly with hardware on a computing device, instead of executing on a
host operating system. In one of these embodiments, the hypervisor 401
may be said to be executing on "bare metal," referring to the hardware
comprising the computing device.

[0154] In some embodiments, a hypervisor 401 may create a virtual machine
406a-c (generally 406) in which an operating system 410 executes. In one
of these embodiments, for example, the hypervisor 401 loads a virtual
machine image to create a virtual machine 406. In another of these
embodiments, the hypervisor 401 executes an operating system 410 within
the virtual machine 406. In still another of these embodiments, the
virtual machine 406 executes an operating system 410.

[0155] In some embodiments, the hypervisor 401 controls processor
scheduling and memory partitioning for a virtual machine 406 executing on
the computing device 100. In one of these embodiments, the hypervisor 401
controls the execution of at least one virtual machine 406. In another of
these embodiments, the hypervisor 401 presents at least one virtual
machine 406 with an abstraction of at least one hardware resource
provided by the computing device 100. In other embodiments, the
hypervisor 401 controls whether and how physical processor capabilities
are presented to the virtual machine 406.

[0156] A control operating system 405 may execute at least one application
for managing and configuring the guest operating systems. In one
embodiment, the control operating system 405 may execute an
administrative application, such as an application including a user
interface providing administrators with access to functionality for
managing the execution of a virtual machine, including functionality for
executing a virtual machine, terminating an execution of a virtual
machine, or identifying a type of physical resource for allocation to the
virtual machine. In another embodiment, the hypervisor 401 executes the
control operating system 405 within a virtual machine 406 created by the
hypervisor 401. In still another embodiment, the control operating system
405 executes in a virtual machine 406 that is authorized to directly
access physical resources on the computing device 100. In some
embodiments, a control operating system 405a on a computing device 100a
may exchange data with a control operating system 405b on a computing
device 100b, via communications between a hypervisor 401a and a
hypervisor 401b. In this way, one or more computing devices 100 may
exchange data with one or more of the other computing devices 100
regarding processors and other physical resources available in a pool of
resources. In one of these embodiments, this functionality allows a
hypervisor to manage a pool of resources distributed across a plurality
of physical computing devices. In another of these embodiments, multiple
hypervisors manage one or more of the guest operating systems executed on
one of the computing devices 100.

[0157] In one embodiment, the control operating system 405 executes in a
virtual machine 406 that is authorized to interact with at least one
guest operating system 410. In another embodiment, a guest operating
system 410 communicates with the control operating system 405 via the
hypervisor 401 in order to request access to a disk or a network. In
still another embodiment, the guest operating system 410 and the control
operating system 405 may communicate via a communication channel
established by the hypervisor 401, such as, for example, via a plurality
of shared memory pages made available by the hypervisor 401.

[0158] In some embodiments, the control operating system 405 includes a
network back-end driver for communicating directly with networking
hardware provided by the computing device 100. In one of these
embodiments, the network back-end driver processes at least one virtual
machine request from at least one guest operating system 110. In other
embodiments, the control operating system 405 includes a block back-end
driver for communicating with a storage element on the computing device
100. In one of these embodiments, the block back-end driver reads and
writes data from the storage element based upon at least one request
received from a guest operating system 410.

[0159] In one embodiment, the control operating system 405 includes a
tools stack 404. In another embodiment, a tools stack 404 provides
functionality for interacting with the hypervisor 401, communicating with
other control operating systems 405 (for example, on a second computing
device 100b), or managing virtual machines 406b, 406c on the computing
device 100. In another embodiment, the tools stack 404 includes
customized applications for providing improved management functionality
to an administrator of a virtual machine farm. In some embodiments, at
least one of the tools stack 404 and the control operating system 405
include a management API that provides an interface for remotely
configuring and controlling virtual machines 406 running on a computing
device 100. In other embodiments, the control operating system 405
communicates with the hypervisor 401 through the tools stack 404.

[0160] In one embodiment, the hypervisor 401 executes a guest operating
system 410 within a virtual machine 406 created by the hypervisor 401. In
another embodiment, the guest operating system 410 provides a user of the
computing device 100 with access to resources within a computing
environment. In still another embodiment, a resource includes a program,
an application, a document, a file, a plurality of applications, a
plurality of files, an executable program file, a desktop environment, a
computing environment, or other resource made available to a user of the
computing device 100. In yet another embodiment, the resource may be
delivered to the computing device 100 via a plurality of access methods
including, but not limited to, conventional installation directly on the
computing device 100, delivery to the computing device 100 via a method
for application streaming, delivery to the computing device 100 of output
data generated by an execution of the resource on a second computing
device 100' and communicated to the computing device 100 via a
presentation layer protocol, delivery to the computing device 100 of
output data generated by an execution of the resource via a virtual
machine executing on a second computing device 100', or execution from a
removable storage device connected to the computing device 100, such as a
USB device, or via a virtual machine executing on the computing device
100 and generating output data. In some embodiments, the computing device
100 transmits output data generated by the execution of the resource to
another computing device 100'.

[0161] In one embodiment, the guest operating system 410, in conjunction
with the virtual machine on which it executes, forms a fully-virtualized
virtual machine which is not aware that it is a virtual machine; such a
machine may be referred to as a "Domain U HVM (Hardware Virtual Machine)
virtual machine". In another embodiment, a fully-virtualized machine
includes software emulating a Basic Input/Output System (BIOS) in order
to execute an operating system within the fully-virtualized machine. In
still another embodiment, a fully-virtualized machine may include a
driver that provides functionality by communicating with the hypervisor
401. In such an embodiment, the driver may be aware that it executes
within a virtualized environment. In another embodiment, the guest
operating system 410, in conjunction with the virtual machine on which it
executes, forms a paravirtualized virtual machine, which is aware that it
is a virtual machine; such a machine may be referred to as a "Domain U PV
virtual machine". In another embodiment, a paravirtualized machine
includes additional drivers that a fully-virtualized machine does not
include. In still another embodiment, the paravirtualized machine
includes the network back-end driver and the block back-end driver
included in a control operating system 405, as described above.

[0162] Referring now to FIG. 4B, a block diagram depicts one embodiment of
a plurality of networked computing devices in a system in which at least
one physical host executes a virtual machine. In brief overview, the
system includes a management component 404 and a hypervisor 401. The
system includes a plurality of computing devices 100, a plurality of
virtual machines 406, a plurality of hypervisors 401, a plurality of
management components referred to variously as tools stacks 404 or
management components 404, and a physical resource 421, 428. The
plurality of physical machines 100 may each be provided as computing
devices 100, described above in connection with FIGS. 1E-1H and 4A.

[0163] In greater detail, a physical disk 428 is provided by a computing
device 100 and stores at least a portion of a virtual disk 442. In some
embodiments, a virtual disk 442 is associated with a plurality of
physical disks 428. In one of these embodiments, one or more computing
devices 100 may exchange data with one or more of the other computing
devices 100 regarding processors and other physical resources available
in a pool of resources, allowing a hypervisor to manage a pool of
resources distributed across a plurality of physical computing devices.
In some embodiments, a computing device 100 on which a virtual machine
406 executes is referred to as a physical host 100 or as a host machine
100.

[0164] The hypervisor executes on a processor on the computing device 100.
The hypervisor allocates, to a virtual disk, an amount of access to the
physical disk. In one embodiment, the hypervisor 401 allocates an amount
of space on the physical disk. In another embodiment, the hypervisor 401
allocates a plurality of pages on the physical disk. In some embodiments,
the hypervisor provisions the virtual disk 442 as part of a process of
initializing and executing a virtual machine 450.

[0165] In one embodiment, the management component 404a is referred to as
a pool management component 404a. In another embodiment, a management
operating system 405a, which may be referred to as a control operating
system 405a, includes the management component. In some embodiments, the
management component is referred to as a tools stack. In one of these
embodiments, the management component is the tools stack 404 described
above in connection with FIG. 4A. In other embodiments, the management
component 404 provides a user interface for receiving, from a user such
as an administrator, an identification of a virtual machine 406 to
provision and/or execute. In still other embodiments, the management
component 404 provides a user interface for receiving, from a user such
as an administrator, the request for migration of a virtual machine 406b
from one physical machine 100 to another. In further embodiments, the
management component 404a identifies a computing device 100b on which to
execute a requested virtual machine 406d and instructs the hypervisor
401b on the identified computing device 100b to execute the identified
virtual machine; such a management component may be referred to as a pool
management component.

[0166] Referring now to FIG. 4C, embodiments of a virtual application
delivery controller or virtual appliance 450 are depicted. In brief
overview, any of the functionality and/or embodiments of the appliance
200 (e.g., an application delivery controller) described above in
connection with FIGS. 2A and 2B may be deployed in any embodiment of the
virtualized environment described above in connection with FIGS. 4A and
4B. Instead of the functionality of the application delivery controller
being deployed in the form of an appliance 200, such functionality may be
deployed in a virtualized environment 400 on any computing device 100,
such as a client 102, server 106 or appliance 200.

[0167] Referring now to FIG. 4C, a diagram of an embodiment of a virtual
appliance 450 operating on a hypervisor 401 of a server 106 is depicted.
As with the appliance 200 of FIGS. 2A and 2B, the virtual appliance 450
may provide functionality for availability, performance, offload and
security. For availability, the virtual appliance may perform load
balancing between layers 4 and 7 of the network and may also perform
intelligent service health monitoring. For performance increases via
network traffic acceleration, the virtual appliance may perform caching
and compression. To offload processing of any servers, the virtual
appliance may perform connection multiplexing and pooling and/or SSL
processing. For security, the virtual appliance may perform any of the
application firewall functionality and SSL VPN function of appliance 200.

[0168] Any of the modules of the appliance 200 as described in connection
with FIG. 2A may be packaged, combined, designed or constructed in a form
of the virtualized appliance delivery controller 450 deployable as one or
more software modules or components executable in a virtualized
environment 300 or non-virtualized environment on any server, such as an
off the shelf server. For example, the virtual appliance may be provided
in the form of an installation package to install on a computing device.
With reference to FIG. 2A, any of the cache manager 232, policy engine
236, compression 238, encryption engine 234, packet engine 240, GUI 210,
CLI 212, shell services 214 and health monitoring programs 216 may be
designed and constructed as a software component or module to run on any
operating system of a computing device and/or of a virtualized
environment 300. Instead of using the encryption processor 260, processor
262, memory 264 and network stack 267 of the appliance 200, the
virtualized appliance 400 may use any of these resources as provided by
the virtualized environment 400 or as otherwise available on the server
106.

[0169] Still referring to FIG. 4C, and in brief overview, any one or more
vServers 275A-275N may be in operation or executed in a virtualized
environment 400 of any type of computing device 100, such as any server
106. Any of the modules or functionality of the appliance 200 described
in connection with FIG. 2B may be designed and constructed to operate in
either a virtualized or non-virtualized environment of a server. Any of
the vServer 275, SSL VPN 280, Intranet UP 282, Switching 284, DNS 286,
acceleration 288, App FW 280 and monitoring agent may be packaged,
combined, designed or constructed in a form of application delivery
controller 450 deployable as one or more software modules or components
executable on a device and/or virtualized environment 400.

[0170] In some embodiments, a server may execute multiple virtual machines
406a-406n in the virtualization environment with each virtual machine
running the same or different embodiments of the virtual application
delivery controller 450. In some embodiments, the server may execute one
or more virtual appliances 450 on one or more virtual machines on a core
of a multi-core processing system. In some embodiments, the server may
execute one or more virtual appliances 450 on one or more virtual
machines on each processor of a multiple processor device.

E. Systems and Methods for Providing A Multi-Core Architecture

[0171] In accordance with Moore's Law, the number of transistors that may
be placed on an integrated circuit may double approximately every two
years. However, CPU speed increases may reach plateaus, for example CPU
speed has been around 3.5-4 GHz range since 2005. In some cases, CPU
manufacturers may not rely on CPU speed increases to gain additional
performance. Some CPU manufacturers may add additional cores to their
processors to provide additional performance. Products, such as those of
software and networking vendors, that rely on CPUs for performance gains
may improve their performance by leveraging these multi-core CPUs. The
software designed and constructed for a single CPU may be redesigned
and/or rewritten to take advantage of a multi-threaded, parallel
architecture or otherwise a multi-core architecture.

[0172] A multi-core architecture of the appliance 200, referred to as
nCore or multi-core technology, allows the appliance in some embodiments
to break the single core performance barrier and to leverage the power of
multi-core CPUs. In the previous architecture described in connection
with FIG. 2A, a single network or packet engine is run. The multiple
cores of the nCore technology and architecture allow multiple packet
engines to run concurrently and/or in parallel. With a packet engine
running on each core, the appliance architecture leverages the processing
capacity of additional cores. In some embodiments, this provides up to a
7× increase in performance and scalability.

[0173] Illustrated in FIG. 5A are some embodiments of work, task, load or
network traffic distribution across one or more processor cores according
to a type of parallelism or parallel computing scheme, such as functional
parallelism, data parallelism or flow-based data parallelism. In brief
overview, FIG. 5A illustrates embodiments of a multi-core system such as
an appliance 200' with n-cores, a total of cores numbers 1 through N. In
one embodiment, work, load or network traffic can be distributed among a
first core 505A, a second core 505B, a third core 505C, a fourth core
505D, a fifth core 505E, a sixth core 505F, a seventh core 505G, and so
on such that distribution is across all or two or more of the n cores
505N (hereinafter referred to collectively as cores 505.) There may be
multiple VIPs 275 each running on a respective core of the plurality of
cores. There may be multiple packet engines 240 each running on a
respective core of the plurality of cores. Any of the approaches used may
lead to different, varying or similar work load or performance level 515
across any of the cores. For a functional parallelism approach, each core
may run a different function of the functionalities provided by the
packet engine, a VIP 275 or appliance 200. In a data parallelism
approach, data may be paralleled or distributed across the cores based on
the Network Interface Card (NIC) or VIP 275 receiving the data. In
another data parallelism approach, processing may be distributed across
the cores by distributing data flows to each core.

[0174] In further detail to FIG. 5A, in some embodiments, load, work or
network traffic can be distributed among cores 505 according to
functional parallelism 500. Functional parallelism may be based on each
core performing one or more respective functions. In some embodiments, a
first core may perform a first function while a second core performs a
second function. In functional parallelism approach, the functions to be
performed by the multi-core system are divided and distributed to each
core according to functionality. In some embodiments, functional
parallelism may be referred to as task parallelism and may be achieved
when each processor or core executes a different process or function on
the same or different data. The core or processor may execute the same or
different code. In some cases, different execution threads or code may
communicate with one another as they work. Communication may take place
to pass data from one thread to the next as part of a workflow.

[0175] In some embodiments, distributing work across the cores 505
according to functional parallelism 500, can comprise distributing
network traffic according to a particular function such as network
input/output management (NW I/O) 510A, secure sockets layer (SSL)
encryption and decryption 510B and transmission control protocol (TCP)
functions 510C. This may lead to a work, performance or computing load
515 based on a volume or level of functionality being used. In some
embodiments, distributing work across the cores 505 according to data
parallelism 540, can comprise distributing an amount of work 515 based on
distributing data associated with a particular hardware or software
component. In some embodiments, distributing work across the cores 505
according to flow-based data parallelism 520, can comprise distributing
data based on a context or flow such that the amount of work 515A-N on
each core may be similar, substantially equal or relatively evenly
distributed.

[0176] In the case of the functional parallelism approach, each core may
be configured to run one or more functionalities of the plurality of
functionalities provided by the packet engine or VIP of the appliance.
For example, core 1 may perform network I/O processing for the appliance
200' while core 2 performs TCP connection management for the appliance.
Likewise, core 3 may perform SSL offloading while core 4 may perform
layer 7 or application layer processing and traffic management. Each of
the cores may perform the same function or different functions. Each of
the cores may perform more than one function. Any of the cores may run
any of the functionality or portions thereof identified and/or described
in conjunction with FIGS. 2A and 2B. In this the approach, the work
across the cores may be divided by function in either a coarse-grained or
fine-grained manner. In some cases, as illustrated in FIG. 5A, division
by function may lead to different cores running at different levels of
performance or load 515.

[0177] In the case of the functional parallelism approach, each core may
be configured to run one or more functionalities of the plurality of
functionalities provided by the packet engine of the appliance. For
example, core 1 may perform network I/O processing for the appliance 200'
while core 2 performs TCP connection management for the appliance.
Likewise, core 3 may perform SSL offloading while core 4 may perform
layer 7 or application layer processing and traffic management. Each of
the cores may perform the same function or different functions. Each of
the cores may perform more than one function. Any of the cores may run
any of the functionality or portions thereof identified and/or described
in conjunction with FIGS. 2A and 2B. In this the approach, the work
across the cores may be divided by function in either a coarse-grained or
fine-grained manner. In some cases, as illustrated in FIG. 5A division by
function may lead to different cores running at different levels of load
or performance.

[0178] The functionality or tasks may be distributed in any arrangement
and scheme. For example, FIG. 5B illustrates a first core, Core 1 505A,
processing applications and processes associated with network I/O
functionality 510A. Network traffic associated with network I/O, in some
embodiments, can be associated with a particular port number. Thus,
outgoing and incoming packets having a port destination associated with
NW I/O 510A will be directed towards Core 1 505A which is dedicated to
handling all network traffic associated with the NW I/O port. Similarly,
Core 2 505B is dedicated to handling functionality associated with SSL
processing and Core 4 505D may be dedicated handling all TCP level
processing and functionality.

[0179] While FIG. 5A illustrates functions such as network I/O, SSL and
TCP, other functions can be assigned to cores. These other functions can
include any one or more of the functions or operations described herein.
For example, any of the functions described in conjunction with FIGS. 2A
and 2B may be distributed across the cores on a functionality basis. In
some cases, a first VIP 275A may run on a first core while a second VIP
275B with a different configuration may run on a second core. In some
embodiments, each core 505 can handle a particular functionality such
that each core 505 can handle the processing associated with that
particular function. For example, Core 2 505B may handle SSL offloading
while Core 4 505D may handle application layer processing and traffic
management.

[0180] In other embodiments, work, load or network traffic may be
distributed among cores 505 according to any type and form of data
parallelism 540. In some embodiments, data parallelism may be achieved in
a multi-core system by each core performing the same task or functionally
on different pieces of distributed data. In some embodiments, a single
execution thread or code controls operations on all pieces of data. In
other embodiments, different threads or instructions control the
operation, but may execute the same code. In some embodiments, data
parallelism is achieved from the perspective of a packet engine, vServers
(VIPs) 275A-C, network interface cards (NIC) 542D-E and/or any other
networking hardware or software included on or associated with an
appliance 200. For example, each core may run the same packet engine or
VIP code or configuration but operate on different sets of distributed
data. Each networking hardware or software construct can receive
different, varying or substantially the same amount of data, and as a
result may have varying, different or relatively the same amount of load
515.

[0181] In the case of a data parallelism approach, the work may be divided
up and distributed based on VIPs, NICs and/or data flows of the VIPs or
NICs. In one of these approaches, the work of the multi-core system may
be divided or distributed among the VIPs by having each VIP work on a
distributed set of data. For example, each core may be configured to run
one or more VIPs. Network traffic may be distributed to the core for each
VIP handling that traffic. In another of these approaches, the work of
the appliance may be divided or distributed among the cores based on
which NIC receives the network traffic. For example, network traffic of a
first NIC may be distributed to a first core while network traffic of a
second NIC may be distributed to a second core. In some cases, a core may
process data from multiple NICs.

[0182] While FIG. 5A illustrates a single vServer associated with a single
core 505, as is the case for VIP1 275A, VIP2 275B and VIP3 275C. In some
embodiments, a single vServer can be associated with one or more cores
505. In contrast, one or more vServers can be associated with a single
core 505. Associating a vServer with a core 505 may include that core 505
to process all functions associated with that particular vServer. In some
embodiments, each core executes a VIP having the same code and
configuration. In other embodiments, each core executes a VIP having the
same code but different configuration. In some embodiments, each core
executes a VIP having different code and the same or different
configuration.

[0183] Like vServers, NICs can also be associated with particular cores
505. In many embodiments, NICs can be connected to one or more cores 505
such that when a NIC receives or transmits data packets, a particular
core 505 handles the processing involved with receiving and transmitting
the data packets. In one embodiment, a single NIC can be associated with
a single core 505, as is the case with NIC1 542D and NIC2 542E. In other
embodiments, one or more NICs can be associated with a single core 505.
In other embodiments, a single NIC can be associated with one or more
cores 505. In these embodiments, load could be distributed amongst the
one or more cores 505 such that each core 505 processes a substantially
similar amount of load. A core 505 associated with a NIC may process all
functions and/or data associated with that particular NIC.

[0184] While distributing work across cores based on data of VIPs or NICs
may have a level of independency, in some embodiments, this may lead to
unbalanced use of cores as illustrated by the varying loads 515 of FIG.
5A.

[0185] In some embodiments, load, work or network traffic can be
distributed among cores 505 based on any type and form of data flow. In
another of these approaches, the work may be divided or distributed among
cores based on data flows. For example, network traffic between a client
and a server traversing the appliance may be distributed to and processed
by one core of the plurality of cores. In some cases, the core initially
establishing the session or connection may be the core for which network
traffic for that session or connection is distributed. In some
embodiments, the data flow is based on any unit or portion of network
traffic, such as a transaction, a request/response communication or
traffic originating from an application on a client. In this manner and
in some embodiments, data flows between clients and servers traversing
the appliance 200' may be distributed in a more balanced manner than the
other approaches.

[0186] In flow-based data parallelism 520, distribution of data is related
to any type of flow of data, such as request/response pairings,
transactions, sessions, connections or application communications. For
example, network traffic between a client and a server traversing the
appliance may be distributed to and processed by one core of the
plurality of cores. In some cases, the core initially establishing the
session or connection may be the core for which network traffic for that
session or connection is distributed. The distribution of data flow may
be such that each core 505 carries a substantially equal or relatively
evenly distributed amount of load, data or network traffic.

[0187] In some embodiments, the data flow is based on any unit or portion
of network traffic, such as a transaction, a request/response
communication or traffic originating from an application on a client. In
this manner and in some embodiments, data flows between clients and
servers traversing the appliance 200' may be distributed in a more
balanced manner than the other approached. In one embodiment, data flow
can be distributed based on a transaction or a series of transactions.
This transaction, in some embodiments, can be between a client and a
server and can be characterized by an IP address or other packet
identifier. For example, Core 1 505A can be dedicated to transactions
between a particular client and a particular server, therefore the load
515A on Core 1 505A may be comprised of the network traffic associated
with the transactions between the particular client and server.
Allocating the network traffic to Core 1 505A can be accomplished by
routing all data packets originating from either the particular client or
server to Core 1 505A.

[0188] While work or load can be distributed to the cores based in part on
transactions, in other embodiments load or work can be allocated on a per
packet basis. In these embodiments, the appliance 200 can intercept data
packets and allocate them to a core 505 having the least amount of load.
For example, the appliance 200 could allocate a first incoming data
packet to Core 1 505A because the load 515A on Core 1 is less than the
load 515B-N on the rest of the cores 505B-N. Once the first data packet
is allocated to Core 1 505A, the amount of load 515A on Core 1 505A is
increased proportional to the amount of processing resources needed to
process the first data packet. When the appliance 200 intercepts a second
data packet, the appliance 200 will allocate the load to Core 4 505D
because Core 4 505D has the second least amount of load. Allocating data
packets to the core with the least amount of load can, in some
embodiments, ensure that the load 515A-N distributed to each core 505
remains substantially equal.

[0189] In other embodiments, load can be allocated on a per unit basis
where a section of network traffic is allocated to a particular core 505.
The above-mentioned example illustrates load balancing on a per/packet
basis. In other embodiments, load can be allocated based on a number of
packets such that every 10, 100 or 1000 packets are allocated to the core
505 having the least amount of load. The number of packets allocated to a
core 505 can be a number determined by an application, user or
administrator and can be any number greater than zero. In still other
embodiments, load can be allocated based on a time metric such that
packets are distributed to a particular core 505 for a predetermined
amount of time. In these embodiments, packets can be distributed to a
particular core 505 for five milliseconds or for any period of time
determined by a user, program, system, administrator or otherwise. After
the predetermined time period elapses, data packets are transmitted to a
different core 505 for the predetermined period of time.

[0190] Flow-based data parallelism methods for distributing work, load or
network traffic among the one or more cores 505 can comprise any
combination of the above-mentioned embodiments. These methods can be
carried out by any part of the appliance 200, by an application or set of
executable instructions executing on one of the cores 505, such as the
packet engine, or by any application, program or agent executing on a
computing device in communication with the appliance 200.

[0191] The functional and data parallelism computing schemes illustrated
in FIG. 5A can be combined in any manner to generate a hybrid parallelism
or distributed processing scheme that encompasses function parallelism
500, data parallelism 540, flow-based data parallelism 520 or any
portions thereof. In some cases, the multi-core system may use any type
and form of load balancing schemes to distribute load among the one or
more cores 505. The load balancing scheme may be used in any combination
with any of the functional and data parallelism schemes or combinations
thereof.

[0192] Illustrated in FIG. 5B is an embodiment of a multi-core system 545,
which may be any type and form of one or more systems, appliances,
devices or components. This system 545, in some embodiments, can be
included within an appliance 200 having one or more processing cores
505A-N. The system 545 can further include one or more packet engines
(PE) or packet processing engines (PPE) 548A-N communicating with a
memory bus 556. The memory bus may be used to communicate with the one or
more processing cores 505A-N. Also included within the system 545 can be
one or more network interface cards (NIC) 552 and a flow distributor 550
which can further communicate with the one or more processing cores
505A-N. The flow distributor 550 can comprise a Receive Side Scaler (RSS)
or Receive Side Scaling (RSS) module 560.

[0193] Further referring to FIG. 5B, and in more detail, in one embodiment
the packet engine(s) 548A-N can comprise any portion of the appliance 200
described herein, such as any portion of the appliance described in FIGS.
2A and 2B. The packet engine(s) 548A-N can, in some embodiments, comprise
any of the following elements: the packet engine 240, a network stack
267; a cache manager 232; a policy engine 236; a compression engine 238;
an encryption engine 234; a GUI 210; a CLI 212; shell services 214;
monitoring programs 216; and any other software or hardware element able
to receive data packets from one of either the memory bus 556 or the one
of more cores 505A-N. In some embodiments, the packet engine(s) 548A-N
can comprise one or more vServers 275A-N, or any portion thereof. In
other embodiments, the packet engine(s) 548A-N can provide any
combination of the following functionalities: SSL VPN 280; Intranet UP
282; switching 284; DNS 286; packet acceleration 288; App FW 280;
monitoring such as the monitoring provided by a monitoring agent 197;
functionalities associated with functioning as a TCP stack; load
balancing; SSL offloading and processing; content switching; policy
evaluation; caching; compression; encoding; decompression; decoding;
application firewall functionalities; XML processing and acceleration;
and SSL VPN connectivity.

[0194] The packet engine(s) 548A-N can, in some embodiments, be associated
with a particular server, user, client or network. When a packet engine
548 becomes associated with a particular entity, that packet engine 548
can process data packets associated with that entity. For example, should
a packet engine 548 be associated with a first user, that packet engine
548 will process and operate on packets generated by the first user, or
packets having a destination address associated with the first user.
Similarly, the packet engine 548 may choose not to be associated with a
particular entity such that the packet engine 548 can process and
otherwise operate on any data packets not generated by that entity or
destined for that entity.

[0195] In some instances, the packet engine(s) 548A-N can be configured to
carry out the any of the functional and/or data parallelism schemes
illustrated in FIG. 5A. In these instances, the packet engine(s) 548A-N
can distribute functions or data among the processing cores 505A-N so
that the distribution is according to the parallelism or distribution
scheme. In some embodiments, a single packet engine(s) 548A-N carries out
a load balancing scheme, while in other embodiments one or more packet
engine(s) 548A-N carry out a load balancing scheme. Each core 505A-N, in
one embodiment, can be associated with a particular packet engine 548
such that load balancing can be carried out by the packet engine. Load
balancing may in this embodiment, require that each packet engine 548A-N
associated with a core 505 communicate with the other packet engines
associated with cores so that the packet engines 548A-N can collectively
determine where to distribute load. One embodiment of this process can
include an arbiter that receives votes from each packet engine for load.
The arbiter can distribute load to each packet engine 548A-N based in
part on the age of the engine's vote and in some cases a priority value
associated with the current amount of load on an engine's associated core
505.

[0196] Any of the packet engines running on the cores may run in user
mode, kernel or any combination thereof. In some embodiments, the packet
engine operates as an application or program running is user or
application space. In these embodiments, the packet engine may use any
type and form of interface to access any functionality provided by the
kernel. In some embodiments, the packet engine operates in kernel mode or
as part of the kernel. In some embodiments, a first portion of the packet
engine operates in user mode while a second portion of the packet engine
operates in kernel mode. In some embodiments, a first packet engine on a
first core executes in kernel mode while a second packet engine on a
second core executes in user mode. In some embodiments, the packet engine
or any portions thereof operates on or in conjunction with the NIC or any
drivers thereof.

[0197] In some embodiments the memory bus 556 can be any type and form of
memory or computer bus. While a single memory bus 556 is depicted in FIG.
5B, the system 545 can comprise any number of memory buses 556. In one
embodiment, each packet engine 548 can be associated with one or more
individual memory buses 556.

[0198] The NIC 552 can in some embodiments be any of the network interface
cards or mechanisms described herein. The NIC 552 can have any number of
ports. The NIC can be designed and constructed to connect to any type and
form of network 104. While a single NIC 552 is illustrated, the system
545 can comprise any number of NICs 552. In some embodiments, each core
505A-N can be associated with one or more single NICs 552. Thus, each
core 505 can be associated with a single NIC 552 dedicated to a
particular core 505. The cores 505A-N can comprise any of the processors
described herein. Further, the cores 505A-N can be configured according
to any of the core 505 configurations described herein. Still further,
the cores 505A-N can have any of the core 505 functionalities described
herein. While FIG. 5B illustrates seven cores 505A-G, any number of cores
505 can be included within the system 545. In particular, the system 545
can comprise "N" cores, where "N" is a whole number greater than zero.

[0199] A core may have or use memory that is allocated or assigned for use
to that core. The memory may be considered private or local memory of
that core and only accessible by that core. A core may have or use memory
that is shared or assigned to multiple cores. The memory may be
considered public or shared memory that is accessible by more than one
core. A core may use any combination of private and public memory. With
separate address spaces for each core, some level of coordination is
eliminated from the case of using the same address space. With a separate
address space, a core can perform work on information and data in the
core's own address space without worrying about conflicts with other
cores. Each packet engine may have a separate memory pool for TCP and/or
SSL connections.

[0200] Further referring to FIG. 5B, any of the functionality and/or
embodiments of the cores 505 described above in connection with FIG. 5A
can be deployed in any embodiment of the virtualized environment
described above in connection with FIGS. 4A and 4B. Instead of the
functionality of the cores 505 being deployed in the form of a physical
processor 505, such functionality may be deployed in a virtualized
environment 400 on any computing device 100, such as a client 102, server
106 or appliance 200. In other embodiments, instead of the functionality
of the cores 505 being deployed in the form of an appliance or a single
device, the functionality may be deployed across multiple devices in any
arrangement. For example, one device may comprise two or more cores and
another device may comprise two or more cores. For example, a multi-core
system may include a cluster of computing devices, a server farm or
network of computing devices. In some embodiments, instead of the
functionality of the cores 505 being deployed in the form of cores, the
functionality may be deployed on a plurality of processors, such as a
plurality of single core processors.

[0201] In one embodiment, the cores 505 may be any type and form of
processor. In some embodiments, a core can function substantially similar
to any processor or central processing unit described herein. In some
embodiment, the cores 505 may comprise any portion of any processor
described herein. While FIG. 5A illustrates seven cores, there can exist
any "N" number of cores within an appliance 200, where "N" is any whole
number greater than one. In some embodiments, the cores 505 can be
installed within a common appliance 200, while in other embodiments the
cores 505 can be installed within one or more appliance(s) 200
communicatively connected to one another. The cores 505 can in some
embodiments comprise graphics processing software, while in other
embodiments the cores 505 provide general processing capabilities. The
cores 505 can be installed physically near each other and/or can be
communicatively connected to each other. The cores may be connected by
any type and form of bus or subsystem physically and/or communicatively
coupled to the cores for transferring data between to, from and/or
between the cores.

[0202] While each core 505 can comprise software for communicating with
other cores, in some embodiments a core manager (not shown) can
facilitate communication between each core 505. In some embodiments, the
kernel may provide core management. The cores may interface or
communicate with each other using a variety of interface mechanisms. In
some embodiments, core to core messaging may be used to communicate
between cores, such as a first core sending a message or data to a second
core via a bus or subsystem connecting the cores. In some embodiments,
cores may communicate via any type and form of shared memory interface.
In one embodiment, there may be one or more memory locations shared among
all the cores. In some embodiments, each core may have separate memory
locations shared with each other core. For example, a first core may have
a first shared memory with a second core and a second share memory with a
third core. In some embodiments, cores may communicate via any type of
programming or API, such as function calls via the kernel. In some
embodiments, the operating system may recognize and support multiple core
devices and provide interfaces and API for inter-core communications.

[0203] The flow distributor 550 can be any application, program, library,
script, task, service, process or any type and form of executable
instructions executing on any type and form of hardware. In some
embodiments, the flow distributor 550 may comprise any design and
construction of circuitry to perform any of the operations and functions
described herein. In some embodiments, the flow distributor distributes,
forwards, routes, controls and/or manages the distribution of data
packets among the cores 505 and/or packet engine or VIPs running on the
cores. The flow distributor 550, in some embodiments, can be referred to
as an interface master. In one embodiment, the flow distributor 550
comprises a set of executable instructions executing on a core or
processor of the appliance 200. In another embodiment, the flow
distributor 550 comprises a set of executable instructions executing on a
computing machine in communication with the appliance 200. In some
embodiments, the flow distributor 550 comprises a set of executable
instructions executing on a NIC, such as firmware. In still other
embodiments, the flow distributor 550 comprises any combination of
software and hardware to distribute data packets among cores or
processors. In one embodiment, the flow distributor 550 executes on at
least one of the cores 505A-N, while in other embodiments a separate flow
distributor 550 assigned to each core 505A-N executes on an associated
core 505A-N. The flow distributor may use any type and form of
statistical or probabilistic algorithms or decision making to balance the
flows across the cores. The hardware of the appliance, such as a NIC, or
the kernel may be designed and constructed to support sequential
operations across the NICs and/or cores.

[0204] In embodiments where the system 545 comprises one or more flow
distributors 550, each flow distributor 550 can be associated with a
processor 505 or a packet engine 548. The flow distributors 550 can
comprise an interface mechanism that allows each flow distributor 550 to
communicate with the other flow distributors 550 executing within the
system 545. In one instance, the one or more flow distributors 550 can
determine how to balance load by communicating with each other. This
process can operate substantially similarly to the process described
above for submitting votes to an arbiter which then determines which flow
distributor 550 should receive the load. In other embodiments, a first
flow distributor 550' can identify the load on an associated core and
determine whether to forward a first data packet to the associated core
based on any of the following criteria: the load on the associated core
is above a predetermined threshold; the load on the associated core is
below a predetermined threshold; the load on the associated core is less
than the load on the other cores; or any other metric that can be used to
determine where to forward data packets based in part on the amount of
load on a processor.

[0205] The flow distributor 550 can distribute network traffic among the
cores 505 according to a distribution, computing or load balancing scheme
such as those described herein. In one embodiment, the flow distributor
can distribute network traffic according to any one of a functional
parallelism distribution scheme 550, a data parallelism load distribution
scheme 540, a flow-based data parallelism distribution scheme 520, or any
combination of these distribution scheme or any load balancing scheme for
distributing load among multiple processors. The flow distributor 550 can
therefore act as a load distributor by taking in data packets and
distributing them across the processors according to an operative load
balancing or distribution scheme. In one embodiment, the flow distributor
550 can comprise one or more operations, functions or logic to determine
how to distribute packers, work or load accordingly. In still other
embodiments, the flow distributor 550 can comprise one or more sub
operations, functions or logic that can identify a source address and a
destination address associated with a data packet, and distribute packets
accordingly.

[0206] In some embodiments, the flow distributor 550 can comprise a
receive-side scaling (RSS) network driver, module 560 or any type and
form of executable instructions which distribute data packets among the
one or more cores 505. The RSS module 560 can comprise any combination of
hardware and software, In some embodiments, the RSS module 560 works in
conjunction with the flow distributor 550 to distribute data packets
across the cores 505A-N or among multiple processors in a multi-processor
network. The RSS module 560 can execute within the NIC 552 in some
embodiments, and in other embodiments can execute on any one of the cores
505.

[0207] In some embodiments, the RSS module 560 uses the MICROSOFT
receive-side-scaling (RSS) scheme. In one embodiment, RSS is a Microsoft
Scalable Networking initiative technology that enables receive processing
to be balanced across multiple processors in the system while maintaining
in-order delivery of the data. The RSS may use any type and form of
hashing scheme to determine a core or processor for processing a network
packet. In other embodiments, the RSS module 560 may employ a different
RSS scheme than the MICROSOFT scheme. For example, the MICROSOFT RSS
scheme may apply to a maximum of 64 processors or cores. In embodiments
where a greater number of cores are used, the RSS module 560 may employ a
different RSS scheme, configured to distribute packets across any number
of cores up to 128, 256, 512, or any other number.

[0208] The RSS module 560 can apply any type and form of hash function
such as the Toeplitz hash function. The hash function may be applied to
the hash type or any of the sequence of values. The hash function may be
a secure hash of any security level or one that is otherwise
cryptographically secure. The hash function may use a hash key. The size
of the key is dependent upon the hash function. For the Toeplitz hash,
the size may be 40 bytes for IPv6 and 16 bytes for IPv4. In some
embodiments, discussed in more detail below, the hash key may be
generated by a random number generator. In other embodiments, the hash
key may be selected from a predetermine list of hash keys. In many
embodiments, the hash key may be generated or selected when the appliance
boots. In other embodiments, the hash key may be generated or selected
once per week, once per day, once per hour, or any other interval of
time.

[0209] The hash function may be designed and constructed based on any one
or more criteria or design goals. In some embodiments, a hash function
may be used that provides an even distribution of hash result for
different hash inputs and different hash types, including TCP/IPv4,
TCP/IPv6, IPv4, and IPv6 headers. In some embodiments, a hash function
may be used that provides a hash result that is evenly distributed when a
small number of buckets are present (for example, two or four). In some
embodiments, hash function may be used that provides a hash result that
is randomly distributed when a large number of buckets were present (for
example, 64 or 128 buckets). In some embodiments, the hash function is
determined based on a level of computational or resource usage. In some
embodiments, the hash function is determined based on ease or difficulty
of implementing the hash in hardware. In some embodiments, the hash
function is determined based on the ease or difficulty of a malicious
remote host to send packets that would all hash to the same bucket.

[0210] The RSS may generate hashes from any type and form of input, such
as a sequence of values. This sequence of values can include any portion
of the network packet, such as any header, field or payload of network
packet, or portions thereof. In some embodiments, the input to the hash
may be referred to as a hash type and include any tuples of information
associated with a network packet or data flow, such as any of the
following: a four tuple comprising at least two IP addresses and two
ports; a four tuple comprising any four sets of values; a six tuple; a
two tuple; and/or any other sequence of numbers or values. The following
are example of hash types that may be used by RSS: [0211] 4-tuple of
source TCP Port, source IP version 4 (IPv4) address, destination TCP
Port, and destination IPv4 address. [0212] 4-tuple of source TCP Port,
source IP version 6 (IPv6) address, destination TCP Port, and destination
IPv6 address. [0213] 2-tuple of source IPv4 address, and destination IPv4
address. [0214] 2-tuple of source IPv6 address, and destination IPv6
address. [0215] 2-tuple of source IPv6 address, and destination IPv6
address, including support for parsing IPv6 extension headers.

[0216] The hash result or any portion thereof may used to identify a core
or entity, such as a packet engine or VIP, for distributing a network
packet. In some embodiments, one or more hash bits or mask are applied to
the hash result. The hash bit or mask may be any number of bits or bytes.
A NIC may support any number of bits, such as six or seven bits. The
network stack may set the actual number of bits to be used during
initialization. The number may be between 1 and 7, inclusive. In other
embodiments, the number may be higher, such as 8 bits or more. In many
embodiments, the number of bits of the mask may be selected based on the
number of processors or cores in a system. For example, 6 bits may be
used in a system supporting less than 2 6 or 64 processors or cores,
while 7 bits may be used in a system supporting up to 2 7 or 128
processors or cores.

[0217] The hash result may be used to identify the core or entity via any
type and form of table, such as a bucket table or indirection table. In
some embodiments, the number of hash-result bits are used to index into
the table. The range of the hash mask may effectively define the size of
the indirection table. Any portion of the hash result or the hast result
itself may be used to index the indirection table. The values in the
table may identify any of the cores or processor, such as by a core or
processor identifier. In some embodiments, all of the cores of the
multi-core system are identified in the table. In other embodiments, a
port of the cores of the multi-core system are identified in the table.
The indirection table may comprise any number of buckets that may be
indexed by a hash mask, such as 2 to 128 buckets. Each bucket may
comprise a range of index values that identify a core or processor. In
some embodiments, the flow controller and/or RSS module may rebalance the
network rebalance the network load by changing the indirection table.

[0218] In some embodiments, the multi-core system 575 does not include a
RSS driver or RSS module 560. In some of these embodiments, a software
steering module (not shown) or a software embodiment of the RSS module
within the system can operate in conjunction with or as part of the flow
distributor 550 to steer packets to cores 505 within the multi-core
system 575.

[0219] The flow distributor 550, in some embodiments, executes within any
module or program on the appliance 200, on any one of the cores 505 and
on any one of the devices or components included within the multi-core
system 575. In some embodiments, the flow distributor 550' can execute on
the first core 505A, while in other embodiments the flow distributor
550'' can execute on the NIC 552. In still other embodiments, an instance
of the flow distributor 550' can execute on each core 505 included in the
multi-core system 575. In this embodiment, each instance of the flow
distributor 550' can communicate with other instances of the flow
distributor 550' to forward packets back and forth across the cores 505.
There exist situations where a response to a request packet may not be
processed by the same core, i.e. the first core processes the request
while the second core processes the response. In these situations, the
instances of the flow distributor 550' can intercept the packet and
forward it to the desired or correct core 505, i.e. a flow distributor
instance 550' can forward the response to the first core. Multiple
instances of the flow distributor 550' can execute on any number of cores
505 and any combination of cores 505.

[0220] The flow distributor may operate responsive to any one or more
rules or policies. The rules may identify a core or packet processing
engine to receive a network packet, data or data flow. The rules may
identify any type and form of tuple information related to a network
packet, such as a 4-tuple of source and destination IP address and source
and destination ports. Based on a received packet matching the tuple
specified by the rule, the flow distributor may forward the packet to a
core or packet engine. In some embodiments, the packet is forwarded to a
core via shared memory and/or core to core messaging.

[0221] Although FIG. 5B illustrates the flow distributor 550 as executing
within the multi-core system 575, in some embodiments the flow
distributor 550 can execute on a computing device or appliance remotely
located from the multi-core system 575. In such an embodiment, the flow
distributor 550 can communicate with the multi-core system 575 to take in
data packets and distribute the packets across the one or more cores 505.
The flow distributor 550 can, in one embodiment, receive data packets
destined for the appliance 200, apply a distribution scheme to the
received data packets and distribute the data packets to the one or more
cores 505 of the multi-core system 575. In one embodiment, the flow
distributor 550 can be included in a router or other appliance such that
the router can target particular cores 505 by altering meta data
associated with each packet so that each packet is targeted towards a
sub-node of the multi-core system 575. In such an embodiment, CISCO's
vn-tag mechanism can be used to alter or tag each packet with the
appropriate meta data.

[0222] Illustrated in FIG. 5C is an embodiment of a multi-core system 575
comprising one or more processing cores 505A-N. In brief overview, one of
the cores 505 can be designated as a control core 505A and can be used as
a control plane 570 for the other cores 505. The other cores may be
secondary cores which operate in a data plane while the control core
provides the control plane. The cores 505A-N may share a global cache
580. While the control core provides a control plane, the other cores in
the multi-core system form or provide a data plane. These cores perform
data processing functionality on network traffic while the control
provides initialization, configuration and control of the multi-core
system.

[0223] Further referring to FIG. 5C, and in more detail, the cores 505A-N
as well as the control core 505A can be any processor described herein.
Furthermore, the cores 505A-N and the control core 505A can be any
processor able to function within the system 575 described in FIG. 5C.
Still further, the cores 505A-N and the control core 505A can be any core
or group of cores described herein. The control core may be a different
type of core or processor than the other cores. In some embodiments, the
control may operate a different packet engine or have a packet engine
configured differently than the packet engines of the other cores.

[0224] Any portion of the memory of each of the cores may be allocated to
or used for a global cache that is shared by the cores. In brief
overview, a predetermined percentage or predetermined amount of each of
the memory of each core may be used for the global cache. For example,
50% of each memory of each code may be dedicated or allocated to the
shared global cache. That is, in the illustrated embodiment, 2 GB of each
core excluding the control plane core or core 1 may be used to form a 28
GB shared global cache. The configuration of the control plane such as
via the configuration services may determine the amount of memory used
for the shared global cache. In some embodiments, each core may provide a
different amount of memory for use by the global cache. In other
embodiments, any one core may not provide any memory or use the global
cache. In some embodiments, any of the cores may also have a local cache
in memory not allocated to the global shared memory. Each of the cores
may store any portion of network traffic to the global shared cache. Each
of the cores may check the cache for any content to use in a request or
response. Any of the cores may obtain content from the global shared
cache to use in a data flow, request or response.

[0225] The global cache 580 can be any type and form of memory or storage
element, such as any memory or storage element described herein. In some
embodiments, the cores 505 may have access to a predetermined amount of
memory (i.e. 32 GB or any other memory amount commensurate with the
system 575). The global cache 580 can be allocated from that
predetermined amount of memory while the rest of the available memory can
be allocated among the cores 505. In other embodiments, each core 505 can
have a predetermined amount of memory. The global cache 580 can comprise
an amount of the memory allocated to each core 505. This memory amount
can be measured in bytes, or can be measured as a percentage of the
memory allocated to each core 505. Thus, the global cache 580 can
comprise 1 GB of memory from the memory associated with each core 505, or
can comprise 20 percent or one-half of the memory associated with each
core 505. In some embodiments, only a portion of the cores 505 provide
memory to the global cache 580, while in other embodiments the global
cache 580 can comprise memory not allocated to the cores 505.

[0226] Each core 505 can use the global cache 580 to store network traffic
or cache data. In some embodiments, the packet engines of the core use
the global cache to cache and use data stored by the plurality of packet
engines. For example, the cache manager of FIG. 2A and cache
functionality of FIG. 2B may use the global cache to share data for
acceleration. For example, each of the packet engines may store
responses, such as HTML data, to the global cache. Any of the cache
managers operating on a core may access the global cache to server caches
responses to client requests.

[0227] In some embodiments, the cores 505 can use the global cache 580 to
store a port allocation table which can be used to determine data flow
based in part on ports. In other embodiments, the cores 505 can use the
global cache 580 to store an address lookup table or any other table or
list that can be used by the flow distributor to determine where to
direct incoming and outgoing data packets. The cores 505 can, in some
embodiments read from and write to cache 580, while in other embodiments
the cores 505 can only read from or write to cache 580. The cores may use
the global cache to perform core to core communications.

[0228] The global cache 580 may be sectioned into individual memory
sections where each section can be dedicated to a particular core 505. In
one embodiment, the control core 505A can receive a greater amount of
available cache, while the other cores 505 can receiving varying amounts
or access to the global cache 580.

[0229] In some embodiments, the system 575 can comprise a control core
505A. While FIG. 5C illustrates core 1 505A as the control core, the
control core can be any core within the appliance 200 or multi-core
system. Further, while only a single control core is depicted, the system
575 can comprise one or more control cores each having a level of control
over the system. In some embodiments, one or more control cores can each
control a particular aspect of the system 575. For example, one core can
control deciding which distribution scheme to use, while another core can
determine the size of the global cache 580.

[0230] The control plane of the multi-core system may be the designation
and configuration of a core as the dedicated management core or as a
master core. This control plane core may provide control, management and
coordination of operation and functionality the plurality of cores in the
multi-core system. This control plane core may provide control,
management and coordination of allocation and use of memory of the system
among the plurality of cores in the multi-core system, including
initialization and configuration of the same. In some embodiments, the
control plane includes the flow distributor for controlling the
assignment of data flows to cores and the distribution of network packets
to cores based on data flows. In some embodiments, the control plane core
runs a packet engine and in other embodiments, the control plane core is
dedicated to management and control of the other cores of the system.

[0231] The control core 505A can exercise a level of control over the
other cores 505 such as determining how much memory should be allocated
to each core 505 or determining which core 505 should be assigned to
handle a particular function or hardware/software entity. The control
core 505A, in some embodiments, can exercise control over those cores 505
within the control plan 570. Thus, there can exist processors outside of
the control plane 570 which are not controlled by the control core 505A.
Determining the boundaries of the control plane 570 can include
maintaining, by the control core 505A or agent executing within the
system 575, a list of those cores 505 controlled by the control core
505A. The control core 505A can control any of the following:
initialization of a core; determining when a core is unavailable;
re-distributing load to other cores 505 when one core fails; determining
which distribution scheme to implement; determining which core should
receive network traffic; determining how much cache should be allocated
to each core; determining whether to assign a particular function or
element to a particular core; determining whether to permit cores to
communicate with one another; determining the size of the global cache
580; and any other determination of a function, configuration or
operation of the cores within the system 575.

F. Systems and Methods for Generating Cookie Signatures for Security
Protection in a Multi-Core System

[0232] Before discussing the specifics of cookie signatures, it may be
helpful to first describe a few types of malicious attacks for which
cookies are used for protection. Synchronization (SYN) attacks, sometimes
called SYN floods, and HTTP Denial of Service (HTTP DoS) attacks are two
similar methods that malicious attackers can use to slow down or disable
a remote server by tying up memory and resources to prevent innocent
users from accessing said resources.

[0233] In the standard 3-way handshaking protocol of TCP and similar
transport layer protocols, a client requests a connection by sending a
SYN message to a server or appliance. Classically, the server or
appliance allocates memory and/or resources to a client-side socket, and
responds with an acknowledgement message (SYN-ACK). The client then
responds with an acknowledgement (ACK) and the connection is established.

[0234] In the SYN flood or SYN attack, a malicious client or clients send
a plurality of SYN requests. As is usual, the appliance or server
allocates memory and resources for each request and responds with SYN-ACK
messages. The malicious client never responds to these SYN-ACK messages
with acknowledgement messages, and the connections are not established.
Rather, the server or appliance remains in a listening state waiting for
the acknowledgement messages from the client or clients, and the memory
and resources stay allocated to these connections, until the server or
appliance times out, which may be several minutes.

[0235] One solution proposed for SYN floods was to simply not allocate the
resources on the server or appliance until the client responds to the
SYN-ACK message. However, the server or appliance must still remember
which clients have received which SYN-ACK messages so that when a
corresponding ACK arrives, the server or appliance may respond properly.
Accordingly, a small amount of data regarding the connection is stored in
a SYN queue. As more SYN requests come in, the SYN queue can become
overloaded. Some systems will ignore further SYN requests, including
those from legitimate users; other systems remove the oldest SYN requests
in the SYN queue, which again, may be from legitimate users. A further
solution is to increase the size of the SYN queue. However, this may be
undesirable.

[0236] The use of SYN cookies is an alternate solution that avoids the use
of the SYN queue in cases of overflow. Information that would be placed
in the SYN queue as an entry for any particular SYN request is instead
encoded into the initial sequence number transmitted in the SYN-ACK
packet to the client. If an ACK packet is later received from the client
acknowledging the initial sequence number, the server or appliance may
decode from the sequence number the original information. This also
prevents an extension of the TCP flood attack, in which a malicious
attacker sends acknowledgement packets with spoofed IP addresses to forge
a connection to another host. Because these seem to be legitimate
connections to the server, memory and resources are allocated to a
connection that doesn't actually exist. By including a secret key value
in the encoded initial sequence number, the server can ignore
acknowledgement packets that don't include the encoded secret key, making
it prohibitively difficult for a malicious attacker to guess sequence
numbers sent to other IP addresses.

[0237] In many implementations of SYN cookies, the initial sequence number
(ISN) for a SYN-ACK packet is determined by using a hash function, such
as MD5, on an input of the source IP and port and destination IP and port
indicated by the original SYN request, along with one or more random
numbers provided by a random or pseudo-random number generator. This
value may be concatenated with a number representing the maximum segment
size (MSS) value of the connection, and a timer value that is slowly
increased. The timer value is used to ensure that ISNs increase over
time, as is required by the TCP protocol. In one implementation of SYN
cookies described in IETF RFC 4987, the result may be further
concatenated with a second hash of the source IP and port, destination IP
and port, timer value, and a second random number. When an ACK packet
arrives, the server or appliance may create one or more ISNs for the
source IP and port and destination IP and port indicated in the ACK using
the current or one or more previous timer values and random number values
to determine if the acknowledgement number included in the ACK packet
corresponds to an ISN that could have been created in the last few
minutes. If so, then the server may create a transmission control block
(TCB) for the connection, using the MSS value indicated in the ISN. If
the acknowledgement number of the ACK packet does not correspond to any
ISN, then the ACK packet may be dropped. In many implementations, there
aren't enough bits in the encoded ISN to fully indicate the maximum
segment size for the connection. In these implementations, an index of 8
common MSS values is created, and the closest index value to the MSS
indicated in the SYN request is chosen and encoded in the ISN as a 3-bit
value. In a further implementation of SYN cookies, additional TCP
options, such as window scaling or others may be included in the
timestamp option field. Because a timestamp is echoed by a receiver, if
timestamp options are enabled on a client, it will respond to the SYN-ACK
packet with an ACK including the encoded additional TCP options in the
timestamp echo field, and the server may create a TCB with corresponding
TCP options.

[0238] Thus, in responding to SYN flood attacks, the server or appliance
uses random numbers for entropy in calculating the hash function for the
initial sequence number of SYN-ACK packets. In a multi-core system, this
may present complications. In one implementation in which each core or
packet engine of a multi-core system maintains its own random number
generator or seed from which random numbers are generated, one packet
engine may create a SYN-ACK packet with an ISN from a first random
number, but another packet engine may receive the corresponding ACK
packet. If the second packet engine does not have the same random number
in a cache, the ISNs created by the second packet engine won't correspond
to the ISN in the ACK packet, and the second packet engine will drop the
packet, even though it's from a legitimate client.

[0239] Although discussed above in reference to TCP SYN flood attacks,
similar attacks and corresponding solutions and implementation
difficulties exist with other transport layer protocols.

[0240] A similar attack to the SYN flood is the HTTP Denial of Service
(DoS) attack. In this attack, a malicious attacker or attackers establish
legitimate connections with the appliance or server and send HTTP GET
requests for files. In some implementations, the HTTP GET requests are
incomplete requests, which tie up the server or appliance connection
waiting for the remainder of the request until a timeout value expires.
In other implementations, the GET requests are complete requests for very
large files, which are immediately discarded on receipt by the attacker,
who then issues another GET request. In these implementations, the
attacker will frequently spoof or change his IP address, preventing
successful packet filtering solutions. The same behavior can occur
non-maliciously when a breaking news event leads a large number of users
to request the same data simultaneously, overloading the capabilities of
the server. Worse, a mix of malicious and non-malicious requests
exacerbates the problem.

[0241] Some proposed solutions for the HTTP DoS attack include distributed
caching and precaching and other methods of increasing the ability of the
system to serve content to clients. However, a malicious attacker,
particularly one that is discarding responses, may be able to overload a
system faster than resources may be added to it.

[0242] Another solution takes advantage of the fact that malicious
attackers will drop responses. In implementations of this solution, when
the server or appliance receives an HTTP GET request, it may respond with
an HTTP reply that includes a cookie. In one embodiment, the reply may be
the response requested by the GET request, while in other embodiment, the
reply may be a short response comprising the cookie and a refresh
command, such as a javascript refresh or an http metatag with a refresh
command. This later embodiment may be used, for example, when a large
number of requests arrive simultaneously, so that the server or appliance
may determine if the are legitimate requests or malicious attacks. A
legitimate requestor will reply to the refresh command with a second GET
request, this time including the cookie, while a malicious attacker will
drop the reply without processing it, and generate future GET requests
without the cookie. Thus, the presence of the cookie may be used to
identify a legitimate client.

[0243] In cases where a server or appliance is not currently overloaded
with requests, the server or appliance may, in some embodiments, still
include the cookie in the response. Future requests from the same client
will include the cookie, up until the time the cookie expires, the client
cache is cleared, or a new cookie is set. During a later HTTP DoS attack,
the server or appliance may service requests from this client with a
higher priority, knowing that the client was, at least at one prior time,
a legitimate client rather than a malicious attacker.

[0244] In many embodiments, the cookie used in these implementations is
generated from a hash function with a random seed that is changed
frequently. This decreases the likelihood of a malicious attacker being
able to receive a first cookie in response to a request, and then
generate a plurality of requests by reusing the cookie or guessing future
cookies. In one such embodiment, the server or appliance maintains an
array of cookie signatures. This array may be any size, depending on the
amount of entropy and frequency of cookie variance desired. In one
implementation, the cookie array may include 64, 128, 192, 256, or more
cookie signatures, each of 8, 16, 24, 32, 40, or more bits in length. In
some implementations, the cookie may be generated by concatenating one or
more cookie signatures from the array. In another implementation, the
cookie may be generated by applying a hash function to one or more cookie
signatures from the array. In many implementations, a pointer within the
array is advanced, or the values of the array are rotated, such that each
successive cookie uses one or more new values from the array.
Additionally, in some implementations, the cookie signature array may be
replaced periodically with a new array. To prevent accidentally treating
legitimate requests with cookies from just before the array was replaced
as malicious, the previous cookie signature array may be temporarily
stored for a period of time. Accordingly, requests containing cookies may
be compared to both the current cookie signature array and the previous
cookie signature array to determine if the request is legitimate.

[0245] Thus, in responding to HTTP DoS attacks, similar to SYN flood
attacks, the server or appliance uses random numbers for entropy in
creating the cookie signature array. As discussed above, in a multi-core
system, this may present complications. In many embodiments, the cookie
signatures of the array are generated by a random number generator or
pseudo-random number generator using a seed. In one implementation in
which each core or packet engine of a multi-core system maintains its own
random number generator or seed from which random numbers are generated,
one packet engine may create a cookie signature array from a first seed
and send a response to a client containing a first cookie, but another
packet engine may receive the next request from the client. If the second
packet engine does not have the same random number in a cache, the cookie
signature array created by the second packet engine won't correspond to
the cookie in the request, and the second packet engine will drop the
packet, even though it's from a legitimate client. As discussed above,
the cookies may be used in transport layer headers, such as in SYN
cookies; in application layer headers, such as in HTTP cookies; or in one
or more headers of one or more layers of the OSI model.

[0246] Shown in FIG. 6 is a system for generating cookie signatures in a
multi-core system. Briefly, appliance 200 may comprise one or more cores
505A-505N, flow distributors 550, and NICs 552, discussed above. Each
core 505A-505N may comprise a packet engine 548A-548N, discussed above, a
timer 600A-600N (referred to generally as timer(s) 600), and a cache
602A-602N (referred to generally as cache(s) 602 or local cache(s) 602).
The appliance may also comprise a shared memory 604, which may be part of
a main memory 122, cache 140, storage 128, or any other memory element
similar to those discussed herein. In some embodiments, the shared memory
604 may comprise a random seed 606, which may also be referred to as a
global random seed 606. Each cache of the one or more caches 602 may
comprise a random seed 608, which may also be referred to as a local
random seed 608. Each cache may further comprise a current cookie
signature 610A-610N (referred to generally as current cookie signature(s)
610) and a previous cookie signature 612A-612N (referred to generally as
previous cookie signature(s) 612). Appliance 200 may also comprise one or
more random number generators or pseudo-random number generators (not
shown), which may use an internal or external source of entropy. In some
embodiments, a random number generator may comprise a function,
subroutine, or service executed by a packet engine 548.

[0247] Still referring to FIG. 6 and in more detail, in some embodiments,
each core 505 may be configured with a timer 600. Timer 600 may comprise
a service, daemon, process, function, subroutine, application, or any
type and form of executable instructions for setting and operating a
timer, and sending a notification on expiration of the timer. Timer 600
may comprise hardware, software, or any combination of hardware and
software. In some embodiments, timer 600 may count upwards or downwards
from a first predetermined value to a second predetermined value, and may
count seconds, milliseconds, microseconds, or any interval selected by an
administrator. In some embodiments, timer 600 may be used to initiate a
reset of a global or local random seed, as described below in connection
with FIG. 7A. In many embodiments, timer 600 may comprise a plurality of
timers with different durations, frequencies, or periods, such that
timing of different events is possible.

[0248] In some embodiments, appliance 200 may comprise a shared memory
604. A shared memory 604 may comprise a storage device or element, such
as main memory 122 or cache 140, a global cache 580 discussed above, or
any other type and form of memory element capable of storing a random
seed 606 and accessible by a plurality of cores 505. In some embodiments,
shared memory 604 may comprise a mutex or semaphore. In some embodiments,
shared memory 604 may comprise functionality for locking a shared memory
location, such that a first packet engine or core may write to the
location while other packet engines or cores are prevented from reading
from the location. In other embodiments, the shared memory 604 may
comprise a native integer such that the first packet engine or core may
update the integer with a lockless read-modify-write transaction.

[0249] In some embodiments, a random seed 606 or global random seed 606
may comprise a random or pseudo random number generated by a random or
pseudo-random number generator. In one embodiment, the global random seed
may be an integer of 8, 16, 24, 32 bits or more. In many embodiments, the
global random seed 606 may be generated by a primary packet engine and
placed in the shared memory 604. At intervals dictated by the expiration
of a timer executing on the primary packet engine, the primary packet
engine may generate a new global random seed 606 and replace the global
random seed stored in the shared memory 604.

[0250] In many embodiments, each core 505 may comprise a cache 602. A
cache 602 may comprise a buffer, cache, or memory element, or any other
type and form of memory structure or portion thereof, accessible by a
packet engine executing on a core 505. As shown, a cache 602 may comprise
a local random seed 608, a current cookie signature 610, and a previous
cookie signature 612.

[0251] In some embodiments, a local random seed 608 may comprise a copy of
a global random seed 606, copied to a local cache of each core. In one
such embodiment, when a global random seed 606 has been changed, such as
in response to the expiration of a timer on a primary packet engine, each
packet engine may copy the global random seed 606 into a cache 602 as a
local random seed 608.

[0252] In many embodiments, random seed 608 may be used to construct a
current cookie signature 610. In one embodiment, a current cookie
signature 610 may comprise one or more hash seeds, such as for a SYN
cookie hash as discussed above. In another embodiment, a current cookie
signature 610 may comprise one or more cookie signatures for creation of
an HTTP DoS cookie, as discussed above. In many embodiments, the current
cookie signature 610 may comprise an array of cookie signatures, used for
both SYN and HTTP DoS cookies. The cookie signatures may be created by
using a pseudo-random function, such as the BSD or Linux random( ) or
rand( ) functions, the rand( ) function of Microsoft Windows, or any
other function that creates one or more random numbers. In many
embodiments, the pseudo-random function may be initialized with the
global random seed 606 or local random seed 608 for generating the first
random number, and each successive random number of the array may be
generated using the previous random number as a seed. Because
pseudo-random number generators are deterministic, each packet engine
will generate the same array of cookie signatures provided each starts
from the same random seed. Thus, using a global random seed removes the
need to communicate a large amount of lengthy cookie signatures generated
by a primary packet engine to one or more other packet engines.

[0253] As discussed above, to allow for legitimate requests that arrive
after creation of a new set of cookie signatures to not be discarded,
each cache may comprise a previous cookie signature 612. Before
generating current cookie signatures 610, each packet engine may copy the
array to the previous cookie signature 612, which may then be compared
against incoming requests. Thus, if the global random seed 606 is updated
every minute and a new set of cookie signatures are created, a request
including a cookie signature will have a potential lifetime of two
minutes before becoming invalid. Similarly, if the global random seed 606
is updated every two minutes, a request including a cookie signature will
have a potential lifetime of four minutes before expiring.

[0254] Shown in FIG. 7A is a flow chart of an embodiment of a method of
generating and maintaining consistent cookie signatures in a multi-core
system. Briefly, a primary packet engine may generate a global random
seed at step 700. At step 702, the primary packet engine may store the
global random seed to a local cache. At step 704, the primary packet
engine may store current cookie signatures as previous cookie signatures.
At step 706, the primary packet engine may generate new cookie signatures
from the locally cached random seed. Responsive to the expiration of a
timer at step 708, the primary packet engine may repeat steps 700-708.
Simultaneously, when the global random seed has changed, one or more
other packet engines may store the global random seed to a local cache at
step 702. At step 704, the one or more other packet engines may store
current cookie signatures as previous cookie signatures. At step 706, the
one or more other packet engines may generate new cookie signatures from
the locally cached random seed. Responsive to the expiration of a timer
at step 710, the one or more other packet engines may determine if the
global random seed has changed at step 712. If not, the one or more other
packet engines may repeat steps 710-712. If so, the one or more other
packet engines may repeat steps 702-712. Although one of the packet
engines may be referred to as a primary packet engine, any of the packet
engines may be designated as a primary packet engine in using any of the
techniques and methods described herein.

[0255] Still referring to FIG. 7A and in more detail, at step 700, a
primary packet engine may generate a global random seed. In some
embodiments, generating a global random seed may comprise executing a
function call to generate a random seed, or may comprise requesting a
random number from a random or pseudo-random number generator. In a
further embodiment, generating a global random seed may comprise
accessing a source of entropy, such as a clock timer, a network packet
string, a temperature sensor, a voltage sensor, or any other type and
form of random value that may be used as a seed for a random number
generator. In some embodiments, generating the global random seed may
comprise replacing an existing global random seed stored in a shared
memory.

[0256] At step 702, in some embodiments, the primary packet engine may
store the global random seed to a local cache. In many embodiments, the
primary packet engine may have already stored the global random seed to a
local cache as part of generating the global random seed. Accordingly, in
these embodiments, the primary packet engine may skip this step.

[0257] At step 704, in some embodiments, the primary packet engine may
store the current cookie signatures as a set of previous cookie
signatures. In one embodiment, storing the current cookie signatures as a
set of previous cookie signatures may comprise copying or moving the
current cookie signature array to a different position in memory. In
another embodiment, storing the current cookie signatures as a set of
previous cookie signatures may comprise replacing a previous cookie
signature array.

[0258] At step 706, the primary packet engine may generate a set of new
cookie signatures from the locally-cached random seed. In one embodiment,
generating a set of new cookie signatures may comprise executing a
pseudo-random number function using the locally-cached random seed as an
initial seed to generate the first cookie signature, and generating each
successive cookie signature using the previous cookie signature as a seed
for the pseudo-random number function. In many embodiments, generating a
set of new cookie signatures may comprise generating an array of 64, 128,
192, 256, or more cookie signatures, each of 8, 16, 24, 32, 40, or more
bits in length. In one embodiment, the number of cookie signatures in the
array and length of each cookie signature may be determined by a policy
set by a user or administrator.

[0259] At step 708, responsive to the expiration of a timer, the primary
packet engine may repeat steps 700-708. The long timer period expiring at
step 708 may comprise any value longer than the value of the short timer
period expiring at step 710, discussed below. In one embodiment, the long
timer period may be 10 seconds, 30 seconds, 1 minute, 2 minutes, 5
minutes, any value between these times, or any value longer or shorter,
provided that the period is longer than the value of the short timer
discussed below.

[0260] Still referring to FIG. 7A, one or more other packet engines may,
responsive to the global random seed having been changed by the primary
packet engine, store the global random seed to respective local caches at
step 702. In one embodiment, storing the global random seed to a local
cache may comprise copying the global random seed to a local cache. In an
embodiment in which the primary packet engine locks the shared memory for
reading as part of generating a global random seed at step 700, step 702
may comprise the one or more other packet engines waiting in a spinlock
condition for the global random seed to become unlocked such that they
may copy the global random seed to local caches.

[0261] The one or more other packet engines may, in some embodiments,
store current cookie signatures as previous cookie signatures at step 704
and generate new cookie signatures from a locally-cached random seed at
step 706 as discussed above in connection with the primary packet engine.
As discussed above, because each packet engine generates cookie
signatures starting with an initial value of the global random seed, the
current cookie signature array on each packet engine will be identical
after completion of step 706.

[0262] In response to expiration of a timer at step 710, each packet
engine of the one or more packet engines may determine if the global
random seed has changed at step 712. Due to natural skew of local timers
across a plurality of packet engines as well as processing delays due to
other tasks, in many embodiments where there are multiple packet engines
other than the primary packet engine, each of the one or more other
packet engines may not necessarily execute steps 710 and 712
simultaneously. By selecting a small value for the short timer, each
packet engine will detect a change in the global random seed within a
short time of each other. For example, if the short timer is set to a
period of one second, then at worst one packet engine may detect the
change less than a second after another packet engine. By retaining the
set of previous cookie signatures for the duration of the long timer,
substantially longer than the short timer, then any lag between the
timers of different packet engines becomes inconsequential. As discussed
above, the short timer may be set to any period less than the value of
the longer timer, such as one second, two seconds, or any other value.
The minimum difference between the period of the short timer and the long
timer may be determined based on the time to execute steps 702-706. If
the difference is less than this time, the global random seed may change
faster than the cookie signatures may be updated. However, this is
unlikely to occur in modern, high speed systems unless extreme values are
selected, on the order of nanoseconds.

[0263] At step 712, each of the one or more packet engines may determine,
independently, if the global random seed has changed. In one embodiment,
determining if the global random seed has changed may comprise a packet
engine comparing the global random seed to a locally cached random seed.
If there is no difference and the global random seed has not changed,
then the packet engine may repeat steps 710-712. If the global random
seed has changed, the packet engine may repeat steps 702-712.

[0264] Shown in FIG. 7B is a flow chart of an embodiment of a method of
using cookie signatures for security in a multi-core system. Briefly, at
step 720, a packet engine may receive a request from a client with a
cookie. At step 722, the packet engine may compare cookie signatures of
the request with current and previous cookie signatures. If the request
cookie signatures match the current or previous cookie signatures, then
at step 724 the packet engine may accept and process the request. If the
cookie signature does not match, then the packet engine may determine if
the global random seed has changed, as described above in step 712 of
FIG. 7A. If not, then the packet engine may deny the request at step 726.
However, if the global random seed has changed, then the packet engine
may execute steps 702-706 as described above in FIG. 7A and repeat steps
722-726.

[0265] Still referring to FIG. 7B and in more detail, in some embodiments,
a packet engine may receive a request from a client at step 720. In some
embodiments, the request may not contain a cookie, and the packet engine
may process the request according to other policies. For example, if the
request is a SYN request and does not include a cookie, then the packet
engine may respond with a SYN-ACK including a cookie, as described above.
Similarly, if the request is an HTTP GET request and does not include a
cookie, then the packet engine may respond with the requested file and
include a cookie, or a substitute file with a cookie such as the refresh
command described above, responsive to a policy detecting an attempted
HTTP DoS attack, as described above. In other embodiments, the request
may include a cookie. In some embodiments, cookies are explicit, such as
a cookie value in a header of an HTTP GET request. In other embodiments,
such as in implementations using SYN cookies, cookies are not explicit
but are encoded into an acknowledgement field of an ACK packet. In these
embodiments, the request may be treated as if it has a cookie for the
purpose of the method shown in FIG. 7B.

[0266] At step 722, in some embodiments, the packet engine may compare the
cookie in the request with one or more current and/or previous cookie
signatures. For example, in an embodiment in which the cookie comprises
one or more concatenated cookie signatures of predetermined lengths, the
packet engine may parse the cookie into the one or more cookie
signatures, and then attempt to locate the one or more cookie signatures
in the current cookie signature array. If the packet engine cannot locate
the cookie signatures, then in some embodiments, the packet engine may
attempt to locate the one or more cookie signatures in the previous
cookie signature array.

[0267] In embodiments in which the cookie comprises one or more hash
results, the packet engine may execute a reverse hash function to
determine the cookie signatures. In another embodiment where a reverse
hash function is not available, the packet engine may create one or more
cookies using a hash function and information available in the packet
request. For example, in one implementation of SYN cookies discussed
above, the initial sequence number is selected based on a hash of one or
more of the source IP and port and destination IP and port of the SYN
request, a slowly increasing counter value, and one or more cookie
signatures, and concatenated with a 3-bit encoded MSS value. Accordingly,
in one embodiment, the packet engine may create one or more cookies using
the 3-bit MSS value and a hash of the source IP and port and destination
IP and port of the ACK, the current and previous few counter values based
on the time to live of the SYN-ACK, and one or more cookie signatures
from the current cookie signatures array or previous cookie signatures
array. For example, if the counter value increases once per minute and
the SYN-ACK has a five minute time-to-live, the packet engine may use the
current and previous four counter values in the hash. Each test cookie
may then be compared to the sequence number in the received request to
determine if the sequence number represents a legitimate cookie. In one
embodiment, the sequence number is tested after each test cookie is
created, while in another embodiment, the sequence number is tested after
a set of test cookies are created.

[0268] If the received request contains a legitimate cookie, then at step
724, the request is accepted. Accepting the request may comprise the
packet engine further processing the request; establishing a connection;
allocating memory and/or resources; initializing a transmission control
block or packet control buffer; forwarding the request to a server,
service, or virtual server; or otherwise handling the request. In one
embodiment, in which a server is currently experiencing a flood of HTTP
GET requests due to a DoS attack or a surge due to a breaking news event,
the packet engine may buffer the received request and assign it a higher
priority than other requests because of the legitimate cookie in the
received request.

[0269] If the received request does not contain a cookie signature that
corresponds to a cookie signature in the current cookie signature array
or previous cookie signature array, then at step 712, the packet engine
may determine if the global random seed has changed, using any of the
methods described above in connection with FIG. 7A. If the global random
seed has changed, then in some embodiments, the packet engine may execute
steps 702-706, also described above in connection with FIG. 7A and repeat
steps 722 for the newly generated current cookie signatures.

[0270] If the global random seed has not changed, then at step 726, in
some embodiments, the packet engine may deny the request. In other
embodiments, the packet engine may take other actions, depending on a
policy in place. For example, in an embodiment in which the packet engine
is not currently experiencing a flood of HTTP GET requests, the packet
engine may forward the request or process the request normally. In
another embodiment, in which the packet engine is experiencing a flood of
requests, the packet engine may buffer the received request and assign it
a lower priority than other requests with legitimate cookies. In yet
another embodiment, the packet engine may reply to the received request
with a small response comprising a refresh command and a legitimate
cookie, as described above. Thus, the cookies may be used to ensure
priority processing for legitimate clients while not treating new
legitimate clients who have not yet received cookies as malicious
attackers.

[0271] While various embodiments of the methods and systems have been
described, these embodiments are exemplary and in no way limit the scope
of the described methods or systems. Those having skill in the relevant
art can effect changes to form and details of the described methods and
systems without departing from the broadest scope of the described
methods and systems. Thus, the scope of the methods and systems described
herein should not be limited by any of the exemplary embodiments and
should be defined in accordance with the accompanying claims and their
equivalents.